Visuals as inspiration - mine start simply enough. Witness this mild mannered umbrella that opens out into a demon trap.
Then we get a little bit more complicated. Tell me this sign doesn't cry out for some major backstory. SO MANY BACKSTORIES. The story of the idjits summoning things at Subway - The story of the thing summoned - The story of the poor, beleaguered manager of the Subway shop. "God damn it. I'm trying to make a sandwich and now I've got to clean up another decapitation because you people can't get your séances right? Seriously?"
To this video of awesome that is straight up going in one of my scifi stories because the heroine is a demolitions expert and this is the coolest thing just about ever. Well. Okay. The ping pong balls and liquid nitrogen were cool. But this is definitely a close second. And yes. Things that go BOOM win. I am apparently very easily amused.