I'm not an expert by any means, but yes you could put Batman on a shirt and sell it. I'm not sure how it works for movies, but with audio the actual recordings

I'm not an expert by any means, but yes you could put Batman on a shirt and sell it. I'm not sure how it works for movies, but with audio the actual recordings are still copyrighted for some time after the music itself is in public domain. It would be my guess that any works created after the first one still have copyright on the content itself. Correct me if I'm wrong.