Overall, polka dots suggest joy and whimsy. They also can be associated with pin-up fashion so of course if your bridesmaids like playing a bit of the sexy lady role they're perfect during and after the wedding. The uneven dots pictured below are less bold, more high fashion even sporting stripes at the same time.
Photo 1: via jkoephoto.com
Photo 2: via Grey Likes Weddings
Photos 3&4: via Happy Wedd
Photo 5: via Chic Vintage Brides