A nice idea. I would have liked to have seen better composition, maybe a little more of the car. The photo looks a tad flat and out of focus to me. Good luck with the challenge.
But I don't know what the dog is using the car for. S/he seems merely to be posing on it. The photo, though a pleasing composition, is static. It doesn't seem like part of a movie and doesn't make me want to see what's going to happen (and what has already happened), the way a poster should.