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.
Enclave power helm (fallout) Dark Eldar Kabalite helm( warhammer 40,000) First Dragonborn's Helm( skyrim) Khore Bezerker helmet (warhammer 40,000) Finally, the demon crown of Azhag the Slaughterer (warhammer fantasy.)