I saw this wedding featured over at "Ruffled" blog,and loved this dress.
It's a Carolina Herrera,Garden Party/35806 from Preowned Wedding Dresses.
Here are three pictures from the blog post that I think shows it best.

This one was just sweet,and you get to see the back of it,and how it looks it in that kind of lighting.

You can see the detail of the fabric here.

This one makes the silhouette really pop.