You can practice with these user pictures for the "External picture" option.
It's not that hard to take any picture you have and use practically any photo program.
Just crop it as a square, then reduce size to 48x48 pixels, 60x60 pixels, or 72x72 pixels. 

Don't be alarmed if menu shows as white menu. That can happen if the image got renamed or moved.
If this happens, just put a new location, or select one of the other picture options to clear it. 