Perspective? Easy! + WIP

If you always struggle with perspective like I do, here is great solution: small and easy to use program called Carapace. You can find all information and dowload it here: http://epicgames.com/community/2012/11/free-art-tool-released-thanks-to-epic-friday/
So here is my sketch, done as final home work for Roman's on-line class and its WIP. I've used Carapace to build three vanishing point perspective.
Anyway, Roman corrected it and now I see, that composition isn't so good, and I doubt as for color palette...

sketch:

adding perspective grid:

basic shapes: 

basic colors: