I've heard of this game before; on another forum I belong to, we tried to get one going, but there just wasn't enough interest. Unfortunately now, I don't have to the time to get into it either. If it generates enough interest though, maybe I'll jump in on a later game.
I think the problem you're going to run into there is the passing of the map and everybody using the same software. I agree that GIMP seems to be a good default choice, but I use photoshop and can't say I'm really enthused about learning a new program, even one as supposedly similar to PS as GIMP is.