Read as much mythology as possible would be my advice, and try and get away from anything anyone has used much before. So for example instead of Vamps or Werewolves, create your own or find another myth which can fill the category.
In my book, there are "Elves". However, these "Elves", or Danaan as they call themselves, have a mix of myths associated with them. They are carnivores who live and hunt in small clans, and have no problem with eating humans or even their own kind at a pinch. The weak and sick likewise are simply food. They are more intelligent and faster than humans, although less bulky and not technincally as strong (except that of course they have spent their whole life in the wilds, which means they are generally either at peak fitness or dead, so most of them could maul all but the best trained of human fighters).
The different clans (which are only around 20-30 strong) are all very divided in their ways. Some live closer to nature, and can partially take on the forms of certain animals (Mara, the most important good Danaan character, can posess the minds of hawks or even at need grow wings from her arms). Others live a more civilised existence - in the past of my book, most lands were under the great Bletsungian empire which was formed by the Sun Elves, Danaan who had utterly renounced the forest in favour of creating beauty in works of their own.
I've prolly chucked about 5 or 6 different myths from across Europe into the Danaan. Their name is Irish, from the Tuatha de Danaan, the mythical founders of Ireland. The carnivorous nature is pretty Vampiric, various Germanic spirits can be blamed for most of the rest of their impressive range of abilities.
For your case, there are plenty of good myths which would be fun to mix up here. The scots have a Selkie - the seal maidens, who leave thier skins on the shore each full moon (I think) and come out as a human, then return to the sea at dawn. This could lead to a neat Werewolf variant where they rely on being able to find their wolfskin to be able to turn wolf and hunt with their pack.
Just chucking out ideas, feel more than free to ignore them.
P.S. What do you think of the Danaan as a race, now I've gone and written a bit about them?