If you create something, you can say it's copyrighted and it is. A registered copyright is when you file with the USPTO and can make lawsuits easier because it proves ownership. As is, it is copyrighted but in a civil case the designer (Terry) would have to prove that he came up with it before whoever it was that copied it.
I'm not planning to sell them. Actually, we made an agreement that even if someone brings a Z to him and asks for those, he won't do it because he doesn't do the same car twice, plus they are personalized for me He is a designer though and would be happy to come up with something original for anyone.