I just discovered the RageOn app the other day. It’s still a pretty new community but it’s already TEEMING with stolen fanart. The app is currently only available for iPhone but they also have a web store that has all the same content
The web based store here: http://www.rageon.com/
Their DMCA policy is here: http://www.rageon.com/pages/rageon-dmca-notice-and-takedown-procedure
The DMCA takedown form is here: http://www.rageon.com/pages/rageon-dmca-takedown-form
I just had to send in a takedown form for @hawfstuff ‘s popular Blue Diamond painting so I’m hoping RageOn acts quickly to take it down.