As long it's an formal outfit. That means no tennis shoes, no jeans, no torn t-shirt or usual clothes. Kimono, Lolita outfit are fine.
Cosplay list: Brain Age Guy, Andross (SNES version), Master Hand/Crazy Hand
Animation On Display Game Room Staff and Tournament Co-Director
Sac-Anime Game Room Staff
Fanime E-gaming Staff
Fanime B&W Ball Dance Assistance and Staff 2008-2011
Deviantart ACE Cosplayer