If you create something, it is automatically copyrighted to you, but it's up to you to prove you created it first.
Since the FSM is so famous and, as mentioned, the book was written, there shouldn't be a problem.
A trademark is used for companies selling goods or services. A religion is a belief, so dosen't need to register a trademark.
Images of anything aren't trademarked for any purpose unless they are logos anyway, copyright is the only thing used if that's not the case, whether it's for a religion or not.
Humpty dumpty sat on the wall, humpty dumpty had a great fall... The structure of the wall was incorrect so he won ten grand with Claims Direct!