I like submission #4 the best at this point. I think the yellow Bronco needs to be a little larger or zoomed in. My thoughts are that it would look like the Bronco is moving and is crawling out of the inner circle.
In submission #2 I think I would rather see a cap nut or an acorn nut in the place of the stars. I will try to upload an image of a cap nut and an acorn nut so you understand what I am talking about.