East of Frostmoth, Soltsthiem. See my post on 1st page.
Looks more like the hill around Stormpfund Barrow to me. The twin rock formation gives it away. East of Fort Frostmoth seems to be more thick with trees.
I've only been through MGE Solsthiem once though, and with additional foliage at that. So I'm totally not going to say I couldn't be wrong. Just the hill and rock formations remind me of Stormpfund Barrow.
That's fake! http://i27.lulzimg.com/bfbbe2255d.jpg. Apparently some guy edited it to make it look like skyrim... that's right outside of Frostmoth Keep in Solstheim.
What's funny is the Original looks 10x better and would have had a better chance of passing for a "Skyrim" screenshot if you were almost blind.