[Tkinter] How do I change an image dynamically

[LeeMadeux]

I am trying to dynamically change a displayed picture to another picture on a GUI.
I have tried various suggested ways seen on websites and none have worked this far.
What am I doing wrong?

from tkinter import *
from tkinter import ttk

def TestLogic():
    stgImg = PhotoImage(file="Stage1.gif")
    label=ttk.Label(root, image=stgImg)
    label.image = stgImg
    return

root = Tk()

root.geometry('1010x740+200+200')

stgImg = PhotoImage(file="Stage0.gif")
label=ttk.Label(root, image=stgImg)
label.place(x=400, y=400)

testBtn=ttk.Button(root, text="TEST", command=TestLogic)
testBtn.place(x=400, y=200)
root.mainloop()

The first image is displayed just fine. When I press the button, nothing happens.

Thanks...