You may want to consider whether you've exhausted the 'nasty things' material you already have. Fleshing out your horror may help it come alive (or dead as the case may be)and present new ideas in the process. Think details, backgrounds, odors, the various shades of drying blood, etc. If you've told your readers there's a night sky, for example, have you filled it with stars or clouds?
Personally, I'd avoid collaboration with anyone but your characters at this point. They're not likely to sue for royalties or insist on scenes you'd rather not have written.

I heard of a writer who, upon giving feedback on friends' scripts, would ask to see the rewrite and if ANYTHING was used that resembled something she'd written in her notes, a letter/email would arrive insisting she receive a co-writer byline on the script with legal threats.

It's not worth the hassle. Write a drama or comedy for now and those crazy ideas will start coming to you once you take the pressure off.

"Possibilize" - I didn't realize Sarah Palin wrote scripts, too! Or maybe this was George W....

I'm not a moderator here but...

Can we keep this about screenwriting...

Not political views...

Throw your angst onto the page.

Not here.