Tkinter and PIL: Changing Displayed Image via OptionMenu selection
This is a very common bug. In tkinter, you must keep a reference to the image object or it gets garbage collected.
def changeimage(): path.set(cwd + '/img/' + imageVar.get() + '.png') img = ImageTk.PhotoImage(Image.open(path.get())) panel.configure(image = img) panel.img = img # keep a reference