wow, this is sssooo cool.
I would say... work on the lines a little, but keep the roughness, 'cause that looks great. maybe some shadowing too. looks like your edges got a little cut off their too. this is so cool though!
check out mine if you get a chance.
http://www.threadless.com/critique/82302/Bunny_s_Shadow
OK... Seeing your works, it is a sketch. And a nice one!
Maybe you could help me- and tell me if it is possible to print in the way I coloured my drawing- with so many gradients... and what is there to be done...