I’d like to do something like SO does with profile pictures of new users. It seems to create a unique image based on a value.
How can I repeatedly create the same unique image from a GUID?
I’m open to doing this on the server, but would prefer a client side solution to create it on the fly.
Something like these:

Edit: How can I repeatedly create the same unique “nice looking” image from a GUID?
What you are looking for is called an Identicon.
I think this post might either give you want you want or give you some sample code to look at in order to generate your own images.
http://www.puls200.de/?p=316