I suggest that you don't use the perspective tool but the pen tool, it will reduce aliasing.
The shadows are cutted and they are too much strong.
You may find my comment negative but i'm just telling you how to make it better.
Try also to use some more gradients and vary the tones of colour.
Anyway, it's very good for a first tryout.
I say that because before i only knew how to make small manips. 
EDIT : Grilled by Gandof 360