This Christian Serratos photo contains
demoiselle d'honneur, demoiselle d’honneur, robe de cocktail, gaine, robe de dîner, formel, robe de soirée, and formelle.
There might also be
bouquet, corsage, posy, nosegay, bustier, épaules nues, bretelles, nus, bretelles épaules, and robe.