Background image on a page

Can someone point me in the right direction to do this in v3.01? I'd like to have a background image appear when a particular user logs in, just for their private album. Similar to what the xtreme theme does in v2.

I'm thinking (just a guess) it would take a field in the user db to specify the image, code changes to bring up that image in their private gallery, and also make sure that it only appears in their gallery and not everywhere else.

Any help would be greatly appreciated. Great job on v3. It really is becoming a nice product.