Found this the other day. Couldn't find anything on the forums related to this, so I figured I'd share it and see if maybe anyone else had found any others hidden in the rom.
Go to settings > about phone > then start quickly and repeatedly start tapping on android version until the artwork shows up. Pretty cool, I think.
Edit: I personally haven't tested this on other gingerbread roms, but I wonder if this is liquidgingy specific, or built into gingerbread?
"Zombie art by Jack Larson"