You can see a lot of hands on that link
I didn't use any reference, though the idea of vampires with claws is not new, as seen here
. It is a common belief that vampires have claws, or there wouldn't be this article
. You can find images of vampires with long nails all around the web, in books and in movies. I prefer them with nails as well. It just makes them less human and more.. beast. Along with their aristocratic clothes (yeah, cliché) which underlines everything even better.