Вы можете настроить кнопку с помощью функции конфигурации.
from tkinter import *
master = Tk()
def newFunc():
print ("newclick")
def callback():
print ("oldclick!")
b.configure(image=image_new, text = "New button text", command=newFunc)
image_old = PhotoImage(file=your_imagepath)
image_new = PhotoImage(file=your_second_imagepath)
b = Button(master, image=image_old, text="Button Before click", command=callback)
b.pack()
mainloop()