well first of all...its not YOUR anime con....its a public gathering for people to have fun and dress in costumes/extravagant styles...or even normal clothing.
steampunk is a fashion that is odd compared to normal day standards so people going to cons feel as they will be more accepted there in full out steam punk than in their normal day lives.
its like the goth kids in their hot topic pants with chains ..black hair and lip stick...thats not japanese based fashion..but no one says anything about them.
NDK Cosplay list:
Sailor Cosmos - sailor moon
Secret WCS cosplay <3
season one sailor moon (husband as Tuxedo Mask <3)
and maaaaybe FEM!Lucifer from supernatural