_tkinter.TclError: image "..." doesn't exist

You should use PhotoImage instance as image value. Also, you need to keep the reference of your image.

im = Image.open(pathToImage)
ph = ImageTk.PhotoImage(im)

label = Label(window, image=ph)
label.image=ph  #need to keep the reference of your image to avoid garbage collection

A quick hacky fix is to provide the PhotoImage with the correct master:

i = ImageTk.PhotoImage(pathToImage, master=window)