Well, I would think it would be best if was your own idea.
I mean of course I'm not a prof/board admin, and maybe they'd be okay with ripping someone's work; however, I don't believe so.
If you choose to build off of someone's visual ideas, than you would need to do a ton of research, making tons of additions and subtractions through iteration before calling the result your own. So why not just mind-map to create your own visual ideas?
Of course working off of cliche is a tool, especially if everyone agrees that a certain type of character has a certain type of look to be loosely adhered to, but Concept is key, and often it is considered as important as great execution.