Sorry to say it but the "poor man's copyright", ie: mailing it to yourself is not a legally binding copyright. That's really just a myth. Before you get all bent out of shape about it, I checked with my lawyer and it's the truth. Copyrights are really automatic, ie: you own the rights to whatever you create (as long as it's not a copy of someone else's work). The problem is proving it in a court of law. Your copyright is only as strong as your willingness to defend it. Registering your art work as a "collection" is your cheapest, safest bet. This way you have confirmation from the government that you have "registered" your copyright. You still have to spend your own money to defend your copyright in court. The feds aren't going to do it for you.