Lovely terrain, I've got to say. And that sun, it's nearly outmatching raid1000's sun in his Waterfall Castle terrain, superb, I dont even think I could've done such a great sun.
And yes, the rock formations is... Good most of the time, though I have circled out three spots that I am not too pleased with, I'll do some explaining about what I disapprove of with them.
The closest one marked 2, I just really think you should give it a little more natural look, as of right now it just looks like one rock is mashed on top of the other, as if they were made out of jelly, or something like that.
The furthest away one marked 2, it just really looks unatural, and that's mostly caused by the fact that the mass of rocks on top of those pillars seem to be very thin, and tretchy. Give it some more volume, I'd say.
The one marked 1, is not too much of a problem, if to attend to any of these, I would focus more on the previous two than this one. And honestly, I just dont think it looks too natural, seems static and very... ahh... Unatural to me, but then, that's just my oppinion.
Tile work looks great, dont know why anyone should complain about that. And those brushes could be tinted a little... Browner or yellower to fit in better with the terrain. Finally, I dont really like your cactus on top of the hill to the left, it stands out too much and doesn't look very good, just... remove it
Hope this could be of some help to you
P.S: I'm a hardass paint user today >.>