Как вариант:
import sys
from PyQt5 import QtCore, QtWidgets, QtGui
if __name__ == '__main__':
app = QtWidgets.QApplication(sys.argv)
window = QtWidgets.QWidget()
window.setWindowFlags(QtCore.Qt.Window |
QtCore.Qt.FramelessWindowHint |
QtCore.Qt.WindowStaysOnTopHint)
window.setGeometry(750, 350, 100, 100)
pixmap = QtGui.QPixmap("Ok.png").scaled(100, 100,
QtCore.Qt.KeepAspectRatio,
QtCore.Qt.FastTransformation)
pal = window.palette()
pal.setBrush(QtGui.QPalette.Normal, QtGui.QPalette.Window,
QtGui.QBrush(pixmap))
pal.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.Window,
QtGui.QBrush(pixmap))
window.setPalette(pal)
window.setMask(pixmap.mask())
window.show()
sys.exit(app.exec_())

Ok.png
