Here is bridesmaid dress advice from Vera Wang February 2013:

Not sure how to handle the bridesmaids dresses? Practically speaking, the bride’s attendants will vary in shape and size so choose a common thread to capture the element of pageantry that their role brings to the celebration. I recommend a uniform color or fabric in different silhouettes to flatter each figure and maintain individuality.

Another approach is to ask each attendant to select her own gown (perhaps in a certain color range) to be as inclusive as possible, and will create a connection through a finishing touch such as jewelry, hair or make-up. If color is your connector, remember that pale colors work best for summer weddings and dark colors for winter celebrations. – XO, Vera