Yep, I was pretty wrong there, I have little interest in these types of things, sorry. Design patents do work more like any other patent, so your artwork would have to be rather unique.

So the gullwing doors you probably couldn't patent either. It has to be rather unique. Since this is about something I have little experience with I probably shouldn't try to answer.

Wikipedia: Design patents are subject to both the novelty and non-obviousness standards of the patent code. However, because design patents are not measured based on the utility of the designs to which they are directed, there is an open question as to how to measure the non-obviousness of an ornamental design.