Not to be outdone by our wonderful community, I've had the chance to create some new cover art myself. New disc and case art is up for Twin Sector - a decent little "Portal" clone. Grab it right here:
http://www.steamgamecovers.com/covers/twin-sector
New user @Mub has uploaded a mish-mosh of new covers including a fantastic custom cover for Fallout: New Vegas. You can check out more of @Mub's cover art here:
http://www.steamgamecovers.com/user/Mub
