So one of my friends turned me onto this site while she was on the hunt for her prom dress, and while it's not actually vintage, they have some great, vintage-inspired stuff. I really love their twenties section, especially:
Roaring 20's Ivory/Brown Shimmy Flapper Dress, $198, and Ethereal Ivory/Gold Leaf Twist Dress, $160
They both come in multiple colors, and have a hint of vintage without crossing the line into looking costumey. Wouldn't the flapper dress be an adorable party dress? And I could totally see myself wearing that white dress to a nice beach-side dinner (if I actually went to those).
Brown/white dress: unique-vintage.com
White Dress: unique-vintage.com