Possibly the dumbest idea speculated yet, but I'll throw it out there anyway since I didn't contribute to any of the other crazy ideas for non-horror house that many people will say doesn't belong at the event...
John Wick
It has the gravitas to headline an event, but clearly isn't horror. I don't even know if it's horror adjacent or not, but each movie has about 100 kills by the titular character alone. Sounds pretty horrific. They call Wick the Boogyman (Baba yaga) and he has plenty of signature kills (pencil, horse, library book, dog, car, motorcycle, shotguns, machine guns, about a dozen pistols, axe, assortment of knives, etc).
Definitely NOT horror, but loud gunshot scares and creative deaths could make for an entertaining house.
I think there's maybe a 0.01% chance of it actually happening, but just trying to think of something not really horror, yet has elements of horror (300ish on screen deaths in 3 movies) and is popular enough to headline an event. And yes, I realize how obvious of an answer it is for someone with Neo as their screen name