Well, what you have so far is looking good.
Not too much to go on right now 
Though, I too enjoy modeling little cartoon style cars.
Theres something nice about not having to follow exact blueprints, and to also see what you accidentally come up with
Looking forward to updates!
www.stevenegan-cgi.com
"Your weapons are no match for ours! People of Mars, surrender!"
"Um, this isn't Mars. This is Earth."
"Earth? Earth-with-nuclear-weapons Earth?"
"Yes."
[long pause] "Friend!!"