I too am intrigued, and itchy.
I like the art, it illustrates exactly what it needs to without distracting with anything superfluous...that's gotta be more difficult to pull off than it looks. I know I can't do it.
There is no image in my sig, either because I'm trying to be as unobtrusive as possible, or because I'm too lazy to remember what the hell I did with my banner-thingy. Either or.