The main reason I'm suggesting this is so that I could set my profile image to my facebook image, then both could be changed dynamically. You can get your profile picture from:
http://graph.facebook.com/*YOURUSERNAME*/pictureso there would be no problem with the url changing when profile pictures are updated.
You would also need to add a refresh time for downloading the image for local storage.
I don't know how difficult this would be to add but I'm assuming it can't be too difficult.
EDIT: Also, you can add "?type=" then either square, small or large to define what size image you want to use. Square is 50x50, small is 50 wide with variable height and large is 200 wide with variable height.