In Finland we have this thing called "Wanhojen tanssit". It's a bit like the prom, except that it's held only for the second year students in upper secondary schools. Sorry, I don't really know how to explain it better, but here's a wikipedia article if you really want to know: http://en.wikipedia.org/wiki/Vanhojen_tanssit 'D
My mother wanted to make my dress, so being the usual nerd I am, I gave her a picture of Gwendolyn's gown and told her to make that one. So... it's almost a cosplay costume. I'm only missing a wig, but I'm planning to use this costume in some convention (though right now my cosplay-list for the upcoming year is quite full) so I'll get one later.

Normally my costume maker's pride wouldn't let me wear a dress someone else made, but since mother really wanted and I was in the middle of making Vincent anyway, I made an exception. That, plus I helped with some minor stuff (like cutting the fabric, the petticoat, lacing and I layered the lighter fabric on top) so it's not completely done by someone else. :3

EDIT: Finally, I managed to finish this cosplay. The gown is still sewed mostly by my mother as I stated earlier, but I made the feathery things and styled the wig myself.