Why do churches creep me out? Well, they actually do inspire my writing. Churches have always filled me with dread. The really old ones especially give me chills, and inspiration for horror. I've always seen churches as places where unseen ghostly spirits (think "Holy Ghost") and the supernatural (Angels, dead saints) are invoked for forgiveness, out of fear of eternal punishment for "sinning". In some ancient churches, there are crypts and catacombs filled with dead bodies, and relics made of .... body parts . Who wouldn't be creeped out by that?
What scared me the most were life-sized statues and paintings depicting people covered in blood, pierced by arrows and spears, nailed on crosses, being beheaded, or torn apart by wild animals, their faces with looks of agony and suffering. And the reading of the Bible in churches as the biggest horror novel of all, with genocides, infanticides, Angels killing, drinking of blood and eating of bodies, resurrected corpses, torture by the inquisition, beheadings, etc. All in the name of supernatural beings that supposedly "save" us.
But Churches are where my Vampire Guardian Angels grew up, and often hide, and now they carry on what the inquisition used to do. And they certainly don't need medieval torture devices. If you see a life-sized Angel statue, look closely to see if they are breathing, or if there's blood on their lips. Or fangs.