It's not a standard lib of python 2.7. So in order for these to work properly and if you're using Python 2.7 you should download the PIL library first: Direct download link: http://effbot.org/downloads/PIL-1.1.7.win32-py2.7.exe After installing it, follow these steps:
Edit your script.py
from Tkinter import *
from PIL import ImageTk, Image
app_root = Tk()
#Setting it up
img = ImageTk.PhotoImage(Image.open("app.png"))
#Displaying it
imglabel = Label(app_root, image=img).grid(row=1, column=1)
app_root.mainloop()
Hope that helps!