I like the second dress SpazItUp linked. It's very indicative of the Victorian era, though black was usually used only for mourning. The Victorians used a lot of color. I would do something in grays or blues, and if you wanted black, you could accent it with black lace. Go to trulyvictorian.com and look around at their patterns for some ideas. Or Goggle Victorian fashion plates. You can see that understated was not a word in their vocabulary.
As for accessories, I think it would be cool to wear a necklace that has a small vial of "blood" hanging from it. Wear jewelry that might indicate fangs or something, just little nuances here and there for an overall effect. Sometimes less is more.