import tkinter as tk
from PIL import Image, ImageTk
from Tkinter import *
import Image, ImageTk
import glob,os


def RecentFilePath():
    folder = "C:\\NIR"
    return(str(max((x for x in glob.glob(os.path.join(folder,"*")) if os.path.isfile(x)),key=os.path.getmtime)))

root = tk.Tk()

img = ImageTk.PhotoImage(Image.open('test.png'))
panel = tk.Label(root, image = img)
panel.pack(side = "bottom", fill = "both", expand = "yes")
t = True
def callback():
    global t
    t = not t
    if(t):
        img2 = ImageTk.PhotoImage(Image.open('yubi.PNG'))
    else:
        img2 = ImageTk.PhotoImage(Image.open('test.PNG'))
    panel.configure(image = img2)
    panel.image = img2
    root.after(1000, callback)

root.after(1000, callback)
root.mainloop()