I'll just leave this here
you guys should open the costumes up to the steam workshop, I think that would be cool.
That's a lot of costumes -- personal creativity is always the best, but if you're end up running dry on ideas, look to the TimeSplitters series. I think they managed to play off of /every/ stereotype in existence. ;)
You could call the mode "emperor of the energy sphere" or "space lord of the gravity zone" or "alpha male of the alpha centauri" or something equally stupid.