We already had someone with a right to wear certain gear in a license photo. This was trickier since it involved a prison and the judge said "no, it is a parody." Part of the problem was the litigant didn't say much about his beliefs. As the judge notes, fictional religions (or parodies?) can conceivably be taken seriously. I would rely on that, look at the specific person. Probably borderline. Is non-belief so different from parody advancing same point? Many do it for the fun, but who's to say there isn't also some ultimate beliefs too?