My word, this looks fantastic!
Your environmental/background artwork is great: it emanates a classically bleak, 'dark fairytale' kind of look and whatever you used to achieve the sky really paid off, too. I think it merges well with your background structures; y'know, castles and the like. :D
The shadows and lighting surrounding the protagonist and that monster (animal-skulled, spear-wielding, tribal creature: nice work on the concept by the way!) also draw me to this piece. I suppose what also adds to the perspective involves the foreground plant life. Shading is superb, too.
Even if it is a mock-up, I'm highly impressed. Is it just yourself working on this in-progress game?
Again, I compliment your artistic talent. I'm always rating things too high in my opinion so I tried to find a piece of art that I could criticise, but I can honestly say that I wouldn't change a thing with this one. Animation would certainly further the wondrous graphics and I look forward to your WIP!
Also, may I ask: did you use a tablet to illustrate this? Every artist I ask seems to have one, they seem quite handy. :)
5/5