Вам необходимо использовать wm_attributes:
import tkinter as tk
root = tk.Tk()
# load image
root.image = tk.PhotoImage(file='image.gif')
# disable window movement
root.overrideredirect(True)
# setup start window position
root.geometry("+800+200")
# initialise wm attributes
root.wm_attributes()
# setup transparency
root.wm_attributes("-alpha", 0.5)
# setup label
label = tk.Label(root, image=root.image, bg='white')
label.pack()
label.mainloop()