So I signed up.
Sign-up post and instructions here! Basically you sign up with a fandom (this can change later and can also be original fiction) and pick a horror monster/threat from the list, and after signups close, they email you two related pictures, one or both of which can be used as prompts in addition to the monsters.
It's an incredibly fun fest for me because it's just a little bit different from everything else that's out there, and even when I don't finish anything, which is frequently, I still get a lot of autumn/Halloween feelings and inspiration out of it.
SIXTEEN YEARS, YOU GUYS. I don't know if there's anything other than Yuletide that's been running so long. This entry is also posted at https://sholio.dreamwidth.org/1411034.html with comments.