Try a couble strand of crystal ab accented with gold beads and make matching earrings. It could be done in 4mm with a few 6mm at the middle of the necklace. This will give you sparkle with your black dress. You could also make the 2 strands only the front part of the necklace and have it connect to a gold chain. You could also make a triple strand, two of pearls and one of crystal ab. Use a triple strand clasp. connect the pearls on the two outer and the crystals in the center and then on the other end connect them to one hole over so that the effect is that they over lap each other.
this isn't a very good description. I will try to find a picture or maybe some one can explain it better.

here is a link to necklaces to give you some ideas.

http://www.firemountaingems.com/galleryofdesigns/default.asp