Как сделать так чтобы картинка сохраняла соотношение сторон?

Пожалуйста, всегда предоставляйте минимально-воспроизводимый пример, который демонстрирует проблему.

Как вариант, с использованием виджета QGraphicsView.

import sys
import os.path
from PyQt5.Qt import *


class QtImageViewer(QGraphicsView):
    def __init__(self):
        super().__init__()
        
        self.scene = QGraphicsScene()
        self.setScene(self.scene)
        self._pixmapHandle = None
        self.zoomStack = []
        
        self.aspectRatioMode = Qt.KeepAspectRatio                 # !!!

    def hasImage(self):
        return self._pixmapHandle is not None

    def clearImage(self):
        if self.hasImage():
            self.scene.removeItem(self._pixmapHandle)
            self._pixmapHandle = None

    def pixmap(self):
        if self.hasImage():
            return self._pixmapHandle.pixmap()
        return None

    def image(self):
        if self.hasImage():
            return self._pixmapHandle.pixmap().toImage()
        return None

    def setImage(self, image):
        if type(image) is QPixmap:
            pixmap = image
        elif type(image) is QImage:
            pixmap = QPixmap.fromImage(image)
        else:
            raise RuntimeError(
                "ImageViewer.setImage: Аргумент должен быть QImage или QPixmap.")
        if self.hasImage():
            self._pixmapHandle.setPixmap(pixmap)
        else:
            self._pixmapHandle = self.scene.addPixmap(pixmap)
        self.setSceneRect(QRectF(pixmap.rect()))  
        self.updateViewer()

    def loadImageFromFile(self, fileName=""):
        if len(fileName) == 0:
            fileName, _ = QFileDialog.getOpenFileName(
                self, 
                "Open image file.",
                "",
                "Image files (*.jpg, *.gif, *.png)"
            )

        if len(fileName) and os.path.isfile(fileName):
            image = QImage(fileName)
            self.setImage(image)

    def updateViewer(self):
        if not self.hasImage():
            return
        if len(self.zoomStack) and self.sceneRect().contains(self.zoomStack[-1]):
            self.fitInView(self.zoomStack[-1], Qt.IgnoreAspectRatio)  
        else:
            self.zoomStack = []  
            self.fitInView(self.sceneRect(), self.aspectRatioMode)  

    def resizeEvent(self, event):
        self.updateViewer()


if __name__ == '__main__':
    app = QApplication(sys.argv)
    viewer = QtImageViewer()
    viewer.loadImageFromFile()     
    viewer.show()
    sys.exit(app.exec_())

Ok.png

Вы писали: "Да спасибо, но у меня несколько фреймов в одном Grid"

Вам просто надо встроить мой виджет в свою форму и также
создайте другой класс, который наследуется от соответствующего виджета, и используйте созданный класс для его заполнения вашей формой.

import sys
import os.path
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.Qt import *


class QtImageViewer(QGraphicsView):
    def __init__(self):
        super().__init__()
        
        self.scene = QGraphicsScene()
        self.setScene(self.scene)
        self._pixmapHandle = None
        self.zoomStack = []
        
        self.aspectRatioMode = Qt.KeepAspectRatio                 # !!!
        self.loadImageFromFile("boy33.png")              # "red-apple-fruit-7.png" 

    def hasImage(self):
        return self._pixmapHandle is not None

    def clearImage(self):
        if self.hasImage():
            self.scene.removeItem(self._pixmapHandle)
            self._pixmapHandle = None

    def pixmap(self):
        if self.hasImage():
            return self._pixmapHandle.pixmap()
        return None

    def image(self):
        if self.hasImage():
            return self._pixmapHandle.pixmap().toImage()
        return None

    def setImage(self, image):
        if type(image) is QPixmap:
            pixmap = image
        elif type(image) is QImage:
            pixmap = QPixmap.fromImage(image)
        else:
            raise RuntimeError(
                "ImageViewer.setImage: Аргумент должен быть QImage или QPixmap.")
        if self.hasImage():
            self._pixmapHandle.setPixmap(pixmap)
        else:
            self._pixmapHandle = self.scene.addPixmap(pixmap)
        self.setSceneRect(QRectF(pixmap.rect()))  
        self.updateViewer()

    def loadImageFromFile(self, fileName=""):
        if len(fileName) == 0:
            fileName, _ = QFileDialog.getOpenFileName(
                self, 
                "Open image file.",
                "",
                "Image files (*.jpg, *.gif, *.png)"
            )

        if len(fileName) and os.path.isfile(fileName):
            image = QImage(fileName)
            self.setImage(image)

    def updateViewer(self):
        if not self.hasImage():
            return
        if len(self.zoomStack) and self.sceneRect().contains(self.zoomStack[-1]):
            self.fitInView(self.zoomStack[-1], Qt.IgnoreAspectRatio)  
        else:
            self.zoomStack = []  
            self.fitInView(self.sceneRect(), self.aspectRatioMode)  

    def resizeEvent(self, event):
        self.updateViewer()


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
#        MainWindow.resize(1355, 722)
        sizePolicy = QtWidgets.QSizePolicy(
            QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Preferred)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(MainWindow.sizePolicy().hasHeightForWidth())
#        MainWindow.setSizePolicy(sizePolicy)
# ----------------------------------------------------> vvvvvvvvvvvvv <---------
        MainWindow.setStyleSheet("background-color: rgb(226, 220, 184);")
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        
        self.gridLayout = QtWidgets.QGridLayout(self.centralwidget)
        self.gridLayout.setObjectName("gridLayout")
        self.frame_7 = QtWidgets.QFrame(self.centralwidget)
        self.frame_7.setStyleSheet("background-color: rgb(92, 92, 92);")
        self.frame_7.setFrameShape(QtWidgets.QFrame.StyledPanel)
        self.frame_7.setFrameShadow(QtWidgets.QFrame.Raised)
        self.frame_7.setObjectName("frame_7")
        self.gridLayout.addWidget(self.frame_7, 2, 3, 1, 1)
        
        self.frame_4 = QtWidgets.QFrame(self.centralwidget)
#        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Preferred)
#        sizePolicy.setHorizontalStretch(0)
#        sizePolicy.setVerticalStretch(0)
#        sizePolicy.setHeightForWidth(self.frame_4.sizePolicy().hasHeightForWidth())
#        self.frame_4.setSizePolicy(sizePolicy)
#        self.frame_4.setMinimumSize(QtCore.QSize(325, 0))
#        self.frame_4.setMinimumSize(QtCore.QSize(125, 0))

        self.frame_4.setStyleSheet("background-color: rgb(92, 92, 192);")
        self.frame_4.setFrameShape(QtWidgets.QFrame.StyledPanel)
        self.frame_4.setFrameShadow(QtWidgets.QFrame.Raised)
        self.frame_4.setObjectName("frame_4")
        self.gridLayout.addWidget(self.frame_4, 0, 3, 1, 1)
        
        self.frame_11 = QtWidgets.QFrame(self.centralwidget)
        self.frame_11.setStyleSheet("background-color: rgb(92, 92, 92);")
        self.frame_11.setFrameShape(QtWidgets.QFrame.StyledPanel)
        self.frame_11.setFrameShadow(QtWidgets.QFrame.Raised)
        self.frame_11.setObjectName("frame_11")
        self.gridLayout.addWidget(self.frame_11, 3, 3, 1, 1)

        self.frame_10 = QtWidgets.QFrame(self.centralwidget)
        self.frame_10.setStyleSheet("background-color: rgb(92, 92, 92);")
        self.frame_10.setFrameShape(QtWidgets.QFrame.StyledPanel)
        self.frame_10.setFrameShadow(QtWidgets.QFrame.Raised)
        self.frame_10.setObjectName("frame_10")
        self.gridLayout.addWidget(self.frame_10, 3, 2, 1, 1)
        
        self.frame_9 = QtWidgets.QFrame(self.centralwidget)
        self.frame_9.setStyleSheet("background-color: rgb(92, 92, 92);")
        self.frame_9.setFrameShape(QtWidgets.QFrame.StyledPanel)
        self.frame_9.setFrameShadow(QtWidgets.QFrame.Raised)
        self.frame_9.setObjectName("frame_9")
        self.gridLayout.addWidget(self.frame_9, 3, 1, 1, 1)
        
        self.frame_8 = QtWidgets.QFrame(self.centralwidget)
#        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Preferred, QtWidgets.QSizePolicy.Fixed)
#        sizePolicy.setHorizontalStretch(0)
#        sizePolicy.setVerticalStretch(0)
#        sizePolicy.setHeightForWidth(self.frame_8.sizePolicy().hasHeightForWidth())
#        self.frame_8.setSizePolicy(sizePolicy)
#        self.frame_8.setMinimumSize(QtCore.QSize(0, 77))
        self.frame_8.setStyleSheet("background-color: rgb(92, 92, 92);")
        self.frame_8.setFrameShape(QtWidgets.QFrame.StyledPanel)
        self.frame_8.setFrameShadow(QtWidgets.QFrame.Raised)
        self.frame_8.setObjectName("frame_8")
        self.gridLayout.addWidget(self.frame_8, 3, 0, 1, 1)
        
        self.frame_6 = QtWidgets.QFrame(self.centralwidget)
#        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Preferred, QtWidgets.QSizePolicy.Fixed)
#        sizePolicy.setHorizontalStretch(0)
#        sizePolicy.setVerticalStretch(0)
#        sizePolicy.setHeightForWidth(self.frame_6.sizePolicy().hasHeightForWidth())
#        self.frame_6.setSizePolicy(sizePolicy)
#        self.frame_6.setMinimumSize(QtCore.QSize(0, 127))
        self.frame_6.setStyleSheet("background-color: rgb(92, 92, 92);")
        self.frame_6.setFrameShape(QtWidgets.QFrame.StyledPanel)
        self.frame_6.setFrameShadow(QtWidgets.QFrame.Raised)
        self.frame_6.setObjectName("frame_6")
        self.gridLayout.addWidget(self.frame_6, 2, 2, 1, 1)
        
        self.frame = QtWidgets.QFrame(self.centralwidget)
#        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Fixed)
#        sizePolicy.setHorizontalStretch(0)
#        sizePolicy.setVerticalStretch(0)
#        sizePolicy.setHeightForWidth(self.frame.sizePolicy().hasHeightForWidth())
#        self.frame.setSizePolicy(sizePolicy)
#        self.frame.setMinimumSize(QtCore.QSize(200, 53))
        self.frame.setStyleSheet("background-color: rgb(92, 92, 92);")
        self.frame.setFrameShape(QtWidgets.QFrame.StyledPanel)
        self.frame.setFrameShadow(QtWidgets.QFrame.Raised)
        self.frame.setObjectName("frame")
        self.gridLayout.addWidget(self.frame, 0, 0, 1, 1)
        
        
        self.frame_5 = QtWidgets.QFrame(self.centralwidget)
        self.frame_5.setStyleSheet("background-color: rgb(92, 92, 92);")
        self.frame_5.setFrameShape(QtWidgets.QFrame.StyledPanel)
        self.frame_5.setFrameShadow(QtWidgets.QFrame.Raised)
        self.frame_5.setObjectName("frame_5")
        self.gridLayout.addWidget(self.frame_5, 1, 2, 1, 2)
        
        self.frame_3 = QtWidgets.QFrame(self.centralwidget)
#        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Preferred)
#        sizePolicy.setHorizontalStretch(0)
#        sizePolicy.setVerticalStretch(0)
#        sizePolicy.setHeightForWidth(self.frame_3.sizePolicy().hasHeightForWidth())
#        self.frame_3.setSizePolicy(sizePolicy)
#        self.frame_3.setMinimumSize(QtCore.QSize(334, 0))
        self.frame_3.setStyleSheet("background-color: rgb(92, 92, 92);")
        self.frame_3.setFrameShape(QtWidgets.QFrame.StyledPanel)
        self.frame_3.setFrameShadow(QtWidgets.QFrame.Raised)
        self.frame_3.setObjectName("frame_3")
        self.gridLayout.addWidget(self.frame_3, 0, 2, 1, 1)
        
        self.frame_2 = QtWidgets.QFrame(self.centralwidget)
#        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Preferred)
#        sizePolicy.setHorizontalStretch(0)
#        sizePolicy.setVerticalStretch(0)
#        sizePolicy.setHeightForWidth(self.frame_2.sizePolicy().hasHeightForWidth())
#        self.frame_2.setSizePolicy(sizePolicy)
        self.frame_2.setStyleSheet("background-color: rgb(92, 92, 92);")
        self.frame_2.setFrameShape(QtWidgets.QFrame.StyledPanel)
        self.frame_2.setFrameShadow(QtWidgets.QFrame.Raised)
        self.frame_2.setObjectName("frame_2")
        self.gridLayout.addWidget(self.frame_2, 0, 1, 1, 1)

# !!! +++        
        self.label_13 = QtImageViewer()                               # !!! +++
        self.label_13.setObjectName("label_13")                       # !!! +++
        
        '''
        self.label_13 = QtWidgets.QLabel(self.centralwidget)
        self.label_13.setEnabled(True)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.MinimumExpanding, QtWidgets.QSizePolicy.Expanding)
        sizePolicy.setHorizontalStretch(1)
        sizePolicy.setVerticalStretch(1)
        sizePolicy.setHeightForWidth(self.label_13.sizePolicy().hasHeightForWidth())
        self.label_13.setSizePolicy(sizePolicy)
        self.label_13.setMinimumSize(QtCore.QSize(640, 480))
        self.label_13.setMaximumSize(QtCore.QSize(16777215, 16000000))
        self.label_13.setSizeIncrement(QtCore.QSize(0, 0))
        self.label_13.setBaseSize(QtCore.QSize(0, 0))
        self.label_13.setToolTip("123123")
        self.label_13.setStyleSheet("background-color: rgb(159, 159, 159);")
        self.label_13.setText("")
        self.label_13.setTextFormat(QtCore.Qt.AutoText)
        self.label_13.setPixmap(
            QtGui.QPixmap("red-apple-fruit-7.png"))
        self.label_13.setScaledContents(True)
        self.label_13.setAlignment(QtCore.Qt.AlignCenter)
        self.label_13.setObjectName("label_13")
        '''
        
        self.gridLayout.addWidget(self.label_13, 1, 0, 2, 2, alignment=Qt.AlignCenter)
        
        MainWindow.setCentralWidget(self.centralwidget)
#        self.statusbar = QtWidgets.QStatusBar(MainWindow)
#        self.statusbar.setObjectName("statusbar")
#        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", ""))


# +++ vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
class MainWindow(QMainWindow, Ui_MainWindow):
    def __init__(self):
        super().__init__()
        self.setupUi(self)
        
        label_7 = QLabel('frame_7,  2, 3, 1, 1', self.frame_7)
        label_4 = QLabel('frame_4,  0, 3, 1, 1', self.frame_4)
        label_11 = QLabel('frame_11, 3, 3, 1, 1', self.frame_11)
        label_10 = QLabel('frame_10, 3, 2, 1, 1', self.frame_10)
        label_9 = QLabel('frame_9, 3, 1, 1, 1', self.frame_9)
        label_8 = QLabel('frame_8, 3, 0, 1, 1', self.frame_8)
        self.frame_8.setMinimumHeight(15)
        label_6 = QLabel('frame_6, 2, 2, 1, 1', self.frame_6)
        label_  = QLabel('frame, 0, 0, 1, 1', self.frame)
        self.frame.setMinimumHeight(15)
        label_5 = QLabel('frame_5, 1, 2, 1, 2', self.frame_5)
        label_3 = QLabel('frame_3, 0, 2, 1, 1', self.frame_3)
        label_2 = QLabel('frame_2, 0, 1, 1, 1', self.frame_2)
        
        self.gridLayout.setRowStretch(0, 1)
        self.gridLayout.setRowStretch(3, 1)
        self.gridLayout.setRowStretch(1, 4)
        self.gridLayout.setRowStretch(2, 2)    
        
        self.gridLayout.setColumnStretch(2, 1)
        self.gridLayout.setColumnStretch(3, 1)
        
        self.gridLayout.setColumnStretch(0, 1)
        self.gridLayout.setColumnStretch(1, 1)

        self.label_13.setStyleSheet("""
            #label_13 { 
                background-color: #e2dcb8;
                border: none;
            }
        """)   
        self.setMinimumWidth(220)
# +++ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        

if __name__ == '__main__':
    app = QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())

boy33.png