[LMH]

If one enters a car in a car show open to the public, I would think the owner has no expectation of privacy for images of his vehicle. That would include anyone who wanted to take photographs of it so long as camera's were permitted in the show by the organizers. The images photographed by a photographer would become his to do with as he pleases, including making them public domain by posting them on the internet. If you don't want your car photographed, don't enter it in a car show.
However, I'm not an attorney and my opinion may not be legally correct. Interesting point of discussion. I'll have to ask a friend who is an attorney and see what he says.
Larry