My dress when I attended my friends' senior prom last year (I scored it on sale!)
Hell Bunny Prom Dress from FairyGothMother - £45
(The oddly shaped back is caused, apparently, by the presence of a large bow. I'd personally remove it if I were going to get this dress.)
Even just finding those examples I was almost overwhelmed by the awesome amount of diversity in prom dresses for us spookies. I can't wait to start looking for mine! Of course, there is also the option of going to thrift stores or making something yourself, so don't think I'm suggesting that you must buy your dress from a retailer, but these just really caught my eye. Because I am only minimally versed in menswear, I cannot help with our gentleman or other suit-wearers, other than to provide you the link to Sinister Sartorialist's Tumblr. Check out his outfit posts, they're quite inspiring!