Your Sebastian cosplay is splendid enough. Ciel or Grell would also be nice. To be honest, I don't remember most of the character names right now, so it is hard for me to make uncommon suggestions. ^^;;
I like the use of color tone, characters, animation, and concept. It is an interesting series and the kind of interest that makes me watch the series until the end.
So, I can't wait for Black Sushi Chef. XD