Looks really really cool.
Made a few small changes, maybe not all of them to your taste, but hopefully something useful there!

1) Made less dense rock texture without the thick outliney shading (was stealing focus a little).
2) Toned down the reds a litttle bit and upped the saturation and contrast on the blues.
3) Made the road area taller, since that's the 'important' area.
4) Added white dots on the tips of the missiles (they were getting a bit lost).
5) Added a little bit of detail on the car, some highlights etc to help it stand out.
Good call on the HUD, might wanna let the user switch between hud on left or right for left handed people too.