The texture is definitely interesting. One thing to incorporate it more into the piece though, would be to add texture to the side of the trunk - in the silhouette. Show where areas stick out. Otherwise it's flat, and looks fake.
So you're saying I need to add more texture to the left, darkest side? I'll see what I can do! :]
@Symbol, I don't really see any lighting issues atm, and it'd help if you told me where I needed to fix the AA.
Anyways, Jalonso helped me out a bit with the clouds and the other shrooms:
He also suggested adding a winding staircase that winds up the mushroom. Would that add some flavor to the piece or what? Thanks for all the comments.