Most Helpful Girl
The dress looks nice on you, but that necklace isn't doing you any good. I suggest you wear a statement necklace like these: www.bbrautkleid.com/.../...BCr-einen-abiball-8.jpg There's a variety to choose from, so you can pick any style you want.
Also, will your shoes be black as well? If so, pick a more colorful necklace to break the monotony, but make sure that it doesn't overshadow your face, so consider your makeup too. If you're planning your makeup to be just simple, then I think it's best you stick with golds, silvers, and whites.
Most Helpful Guy
I like the dress and you look great in it, but like others have said I think of something super elegant when I think of prom. I think if you dress it up with a nice necklace, heels and do you hair nice it will be great.