It would be indeed interesting if it was possible to use symbols of god bought or received at a temple against unholy(or holy if the god is evil) monsters, with power dependent on distance from a temple, number of god followers and faith of the user.
As for vampires, I like their representation in The Witcher(the books, not the game) - they actually come from another dimension to which a rift was briefly opened long ago by magic, and there are many kinds of them:
Ekimm and Fleder - lower vampires, they are beast-like, humanoid monsters, very brutal and pretty dangerous.
Alp - A higher vampire. Takes on a form of a human women, but can also morph into animals like dog or a cat, usually found near villages. Attacks only during full moon at 12' o'clock. It usually sucks blood of sleeping creatures, injecting a sleep-inducing substance causing nightmares. They move perfectly silently
Katakan - A higher vampire. On Kreta and in Greece it's called "happy vampire" as he always shows his white teeth which looks like a smile. Spits blood at his victims; if it touches someone, he starts burning. Usually attacks cows and horses. To kill a katakan, separate him from salt water in which he lives or boil his head in vinegar.
Bruxa - a higher vampire, does not fear sunlight, can attack with sound waves, has sharp fangs and sings after drinking blood. Can transform into a black bat. Attacks during days and nights, looks like a beautiful woman, and is often mistaken with a dryad or an undine. Has skills of charming and telepathy, but to take control over a crearure she must regularly drink it's blood. It mainly fights with high-pitched, incapacitating sounds
Nosferatu - the highest of vampires. Has a human form and can not be killed with ordinary means. Is resistant to heat and fire, can regenerate even after being chopped up and being buried(although this might take many years). During full moon he can transform into a bat. They don't have to drink blood, but usually do it for pleasure - for them it's like drinking alcohol, except better; most of them are practically addicted to it. A nosferatu can easily live among normal humans, but animals can sense that he's not a normal human with his smell.
Oh, and vampires don't multiply by turning others into vampire - as Regis from The Witcher explained - If there were 12 initial vampires and every of them would drink blood of one person at every full moon, there would be 144 new vampires per year, and all these vampires would create 12 vampires each next year, soon the whole world would be vampires, and I'm not even counting geometric increase per month.
Of course these are just examples, but I would really like to see more kinds of vampires in game - a human-like Nosferatu that the player could eventually even make an ally of(by finding out where a one is, you know, gossip about a strange man that dogs bark at, people with fang marks on their necks, but no casaulties, etc.), some lower, brutal vampires assaulting mainly animals living near villages or in sewers, rich nobles having Bruxes as mistresses and perhaps some other kind of higher vampire that could create new vampires(although perhaps need some special ritual and be limited to one or two in lifetime, so the world does not become full of vampires - perhaps one or two dozens per city on average(with cities with no vampires and ones with tons) forming a strict hierarchy based on who created who)
Pardon my eventual poor grammar, but I'm too lazy to spellcheck it(I spent a lot of time writing this, I have no intention of spending even more on correcting it to sound well).