Beautiful forms, and a great, surreal atmosphere, but very busy.
You may wish to tone down the grass tiles a touch, also it might just be my eyes but the colours are slightly hard to look at in combination. I'm not much of a colour kid so my feedback can't really stretch past that.
As well, there is some stylistic dissonance between the block shading of the earth and rocks and the dark outlines of the trees (outlining that I think is flattening them out)
Also small nitpick but the swirl on the stone seems to be out of perspective.
All things considered tho wonderful work, especially for the time-frame you had to work with.