You could do so many different things if you want something '50s inspired.
Siri has BM dresses that come in ivory, like this one:
Vivian Leigh Dress - Siri
You could do actual vintage, as found on a site like Posh Girl Vintage:
Dolly Couture has great '50s inspired gowns (and very good prices), like this one:
Do you know what kind of a neckline you want? Bateau, portrait? Or strapless?
Oh and this Melissa Sweet is gorgeous - a bit more modern (and higher end $$$), but beautiful: