Awesome. Just 2 things I'd change:
-I would put in less scratches on most of the vehicle, and put more in certain areas that are endangered by flying stones etc (around the wheels?)
see here how the bottom part is more dirty/rough/scratched: http://www.panoramio.com/photo/16001889
I think the scratches on yours are a little overdone.
-Put it a little deeper into the sand. Right now it looks too much like it's hovering a little above the sand and is really, really light. (At least that's what it looks like to me)
Other than that, great work.