Not finished yet but give me all the sugestions you can think off! The board it sits on will become a desert diorama with a hand made stone wall, sand, bushes etc.

Looks very good! I would recommend a light dry-brushing of the lightened sand color to help bring out the highlights, and set off the deepening effects of the wash. Try a gentle dusting with a light colored pigment to follow the dry-brushing to give it that stuck-in-the-box look. Great job!

looks pretty good. I would dull up the road wheels, they look like someone armoralled them.