I THOUGHT the pose looked like an MJRanum stock; I was studying one of these poses in his previous series before when I was trying to make (but fail to get off with) a themed picture for AnthroCon. Very nice grunge details on the rocks, BTW
Interesting spot. I just ran the image through 6 search engines* tho and none came up with anything that would suggest the pic was uploaded somewhere else prior. So for now it seems to be staying a mystery.