In Lancôme's ad for the "La vie est belle" perfume with Julia Roberts, the star is seen giving us her sweet All-American smile with only part of her face showing. But what's obvious is the bare back and gorgeous dress she dons. Sweet!
In Harper's Bazaar's The Extras Jewel commercial in the December 2013/January 2014 issue, the Bazaar model dons a contrasting (to Julia's dress) black low back dress in her photo. Doesn't the pose and the sly look just say "Mystery" to you?
Don't shy away from a low back dress especially if you have nice skin. It will help you play a little. ;)