Mance has been cast!
http://insidetv.ew.com/2012/08/17/game-of-thrones-mance-rayder/
Ciar?n Hinds:
http://img2.timeinc.net/ew/i/2012/08/16/CIARAN-HINDS_320x240.jpg
http://www.npr.org/blogs/thetwo-way/2012/06/14/154995693/george-w-bushs-decapitated-head-appeared-on-game-of-thrones?sc=fb&cc=fp
There's a link to the image in there, but it really looks like him. Pretty funny and random.