Можно ли сделать кнопку в Qt Designer прозрачной?

Можно делать по разному, например:

pushButton сделать прозрачным

from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(378, 327)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.gridLayout = QtWidgets.QGridLayout(self.centralwidget)
        self.gridLayout.setObjectName("gridLayout")
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setMinimumSize(QtCore.QSize(100, 100))
        self.pushButton.setStyleSheet("background-color: rgba(255, 255, 255, 0);\n"
"border: none;")
        self.pushButton.setObjectName("pushButton")
        self.gridLayout.addWidget(self.pushButton, 0, 1, 1, 1)
        spacerItem = QtWidgets.QSpacerItem(40, 20, QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Minimum)
        self.gridLayout.addItem(spacerItem, 0, 0, 1, 1)
        spacerItem1 = QtWidgets.QSpacerItem(40, 20, QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Minimum)
        self.gridLayout.addItem(spacerItem1, 0, 2, 1, 1)
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 378, 21))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        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", "MainWindow"))
        self.pushButton.setText(_translate("MainWindow", "PushButton"))

     
        

class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self):                 
        super().__init__()
        
        self.setupUi(self)
        
        # + тут ваша логика
        self.pushButton.clicked.connect(lambda: print(self.pushButton.text()))
        
if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    p = MainWindow()
    p.show()
    sys.exit(app.exec_())

загрузить туда свое .png изображение через интерфейс Qt Designer.

from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(378, 327)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.gridLayout = QtWidgets.QGridLayout(self.centralwidget)
        self.gridLayout.setObjectName("gridLayout")
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setMinimumSize(QtCore.QSize(100, 100))
        self.pushButton.setStyleSheet("background-color: rgba(255, 255, 255, 0);\n"
"border: none;")
        self.pushButton.setText("")
        icon = QtGui.QIcon()
        icon.addPixmap(QtGui.QPixmap("Ok.png"), QtGui.QIcon.Normal, QtGui.QIcon.On)
        self.pushButton.setIcon(icon)
        self.pushButton.setIconSize(QtCore.QSize(100, 100))
        self.pushButton.setShortcut("")
        self.pushButton.setAutoDefault(False)
        self.pushButton.setObjectName("pushButton")
        self.gridLayout.addWidget(self.pushButton, 0, 1, 1, 1)
        spacerItem = QtWidgets.QSpacerItem(40, 20, QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Minimum)
        self.gridLayout.addItem(spacerItem, 0, 0, 1, 1)
        spacerItem1 = QtWidgets.QSpacerItem(40, 20, QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Minimum)
        self.gridLayout.addItem(spacerItem1, 0, 2, 1, 1)
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 378, 21))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        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", "MainWindow"))
     
        

class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self):                 
        super().__init__()
        
        self.setupUi(self)
        
        # + тут ваша логика
        self.pushButton.clicked.connect(lambda: print('clicked'))
        
if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    p = MainWindow()
    p.show()
    sys.exit(app.exec_())