You can always expand I suppose. Almost endlessly it seems, judging from the sheer amount of masked super villains and antiheroes. I think you made a pretty good selection actually. I think I would probably use only one character per movie or comic to make a total of 7 different sources but I must admit I wouldn't want to be forced to choose between the Darth Vader and the trooper helmets.
But ace.
It took me a lot longer to do than I'd care to admit and I'm still sad about leaving out Magneto and Boba Fett, but overall I'm very happy with it!
Well, going from the comments it looks like I had a much wider choice than I thought I did!