Sequencing images using tkinter?

[theteacher.info at gmail.com]

I've started to learn to use tkinter but can't seem to rotate images.

Here is a Python 3.4 program to illustrate the problem. Anyone spot why the for loop doesn't seem to want to display a sucssession of images please? Thanks.

import sys
from tkinter import *
import random
from time import sleep

myGui = Tk()
myGui.geometry("1000x800+400+100")
myGui.title("The Random Machine")

monsters = ["py01.gif", "py02.gif", "py03.gif", "py04.gif", "py05.gif", "py06.gif", "py07.gif", "py08.gif",
            "py09.gif", "py10.gif", "py11.gif", "py12.gif", "py13.gif", "py14.gif", "py15.gif", "py16.gif",
            "py17.gif", "py18.gif", "py19.gif", "py20.gif",]


#Main canvas
canvas1 = Canvas(myGui, width=1000, height=800, bg="white")
canvas1.place(x=0,y=0)


#button
myButton1=Button(canvas1, text='OK', justify = LEFT)

for i in range(10):
   myImage = PhotoImage(file="MonsterImages/Converted/" + random.choice(monsters))
   myButton1.config(image=myImage, width="100", height="200")
   myButton1.place(x=500,y=300)
   sleep(0.2)

myGui.mainloop()