Concerning Intellectual Property on the NES case: We have three main areas that a three dimensional object can fall under...Design patent, Trademark, and Copyright.

Copyright: For the design to be copyright-able it must have no practical utility (such as a statue). Since the NES case has a practical utility (enclosing electronics), it cannot be copyrighted.

Design Patent: The NES was protected under United States design patent D299,726S until Feb 7, 2003 when it expired. There is no longer patent protection for the design.

Trademark: Nintendo can (and may have) protect(ed) the physical NES case design with a trademark (like Coca-cola has done with the shape of their bottle). So, they could very well shut down this little idea if they (a) have trademarked the NES ornamental design and (b) discover this thread and (c) think it's worth their time.

This is just my understanding of US law; though I have researched this type of issue in the past, I'm no attorney.