Just telling you what our legal guys said. They do it every day, i don't. As far as copyrights go i am no expert. I do know that in the world of graphics there is no such thing. You can sell superman t shirts all day long as long as it doesn't say the words "Super Man" on it. I guess the name is the only thing protected. I do know our legal guys are top notch! We deal with all of the giants of the manufacturing industry. From mining equipment manufacturers to nuclear power plants. I would take their advice if i was going to face a judge. Again that was just my two cents, no intent on initiating an argument.
Edit:
Might just be a U.S. thing, not sure but i found this.
http://www.copyright.gov/help/faq/faq-register.htmlAnd this.
§ 411 . Registration and civil infringement actions11
(a) Except for an action brought for a violation of the rights of the author under section 106A(a), and subject to the provisions of subsection (b), no civil action for infringement of the copyright in any United States work shall be instituted until preregistration or registration of the copyright claim has been made in accordance with this title. In any case, however, where the deposit, application, and fee required for registration have been delivered to the Copyright Office in proper form and registration has been refused, the applicant is entitled to institute a civil action for infringement if notice thereof, with a copy of the complaint, is served on the Register of Copyrights. The Register may, at his or her option, become a party to the action with respect to the issue of registrability of the copyright claim by entering an appearance within sixty days after such service, but the Register’s failure to become a party shall not deprive the court of jurisdiction to determine that issue.
Note: I didn't read 106A(a)