We could always have the gallery be composed of all the fan-art that's been posted onto here by our forum-goers in their own art topics. Something like ka's Artbook, albeit a bit more centralized around this forum's art. And trust me, there's a lot of it.
(Actually, now that I think about it, weren't you already trying to gather artwork from users for a main-site gallery almost a year ago? Because it could be something like that.)