One thing I remember reading/seeing about environments is that when you have a path like a river or in your case stairs, that you shouldn't block the entrance like with that rock. I think the reasoning was that it mentally 'blocks' your viewer from traveling through the piece. Haha or something like that
And try to vary your shapes more, most of the them in that environment are straight vertical spikes! It definitely adds to the sinister nature but it would be good to get some more variety.