??? 'Unambiguous' means 'clear as crystal'; in other words, I thought the contest description was more than adequate.
Would it be acceptable to do a figure from a classic line that was planned, but never produced? A customizer wouldn't be able to just make something up, it would have to be a documented thing (prototype photo, sketches, etc.). Here's an example of what I'm talking about: The 1980s Advanced Dungeons & Dragons toy series had a number of unproduced figures including a play set. There are photos of the stuff, but it was never put into production.
http://www.toyarchive.com/DungeonsDragonsPrototypes.html