Key designers ushered in a new wave of au courant styles for Spring 2013, from brilliant bursts of color to fashion-conscious silhouettes to gowns that let their tops down—sort of.

Trend: Portrait Backs
Last season’s sexy backs returned for Spring 2013 with a more demure, romantic attention to delicate embroideries, lace frames, and peekaboo keyholes. “You’re not wearing a two-dimensional dress—people are looking at you from every angle,” says Leonard. “Sheer backs with emb...