As crappy as this example is, you should do what Lucas did with approving the design for Dexter Jetster. He had the ILM'ers sculpt a bunch of maquettes and he picked features of the ones he liked the best and combined them into the Star Wars equivelant of Mel, the cook on TV's Alice.

In other words, maybe you could start with your 10 favorite villians or other costumed characters and start combining items that you like from each. As you mesh them together in your imagination, you should get a pretty cool character.