I am super excited to read anything in any of these fandoms, so thank you for offering!
In general, things I like include villain/heroine dynamics (not necessarily fluffy requited love), fairy tale motifs, bittersweet or hard-won happy endings, female characters front and center, gothic horror, and different-era or genre AUs. (I'm not averse to male-dom BDSM in a story either, so long as it's not a full-on BDSM AU.) You don't have to incorporate any of those things, of course, if you have another idea! I'm not into deathfic (excluding characters who die in canon) or certain kinks (scat, watersports, m-preg, A/B/O).
Matthew Bourne's Sleeping Beauty: A Gothic Romance
This show, you guys. This show. This is what I want out of ballet- gorgeous music and vampiric love triangles! I love Aurora and Leo's young love, and I also love Aurora and Caradoc's creepy captivity dynamic. I'd love to have a fic that shows a little of both! Also, this show is prime for worldbuilding- are these creatures vampires or fairies or what? Are they both? What the hell "tribute" are human kingdoms supposed to pay them? And what is vampire society at large like- there's clearly a lot of them, and they clearly have definite factions.
Hope: The Other Side of Adventure
This game (if that's what it should be called- I'm not even really sure) broke my heart. We've all played so many games with damsels in distress that focus on action, it was just so agonizing to see how she might be feeling as her time runs out and her rescue fails to appear. You could tell me about what happens to the Princess after her rescue, what might have happened if the Duke had won, or what her relationship with the Hero was like- was he goofing around earning acheivements and high scores while she was suffering, or was he really focused on saving her? All I really ask is that you not pin the blame on the Princess for not "standing up for herself" as some reviewers have- I wouldn't have been able to escape from under armed guard, either!
Hammer Horror Films
It sucks to get into a fandom fifty years too late, doesn't it? You don't have to use all four of the characters I nominated (Frankenstein, Van Helsing, Sister Hyde or Marianne), but use at least one...or any combination you desire! (I'm a pretty big Van Helsing/Marianne shipper, personally- that hug at the end of Brides of Dracula really did it for me.) I love Frankenstein's self-centered, womanizing villainy and the fact that he is in no uncertain terms his own monster. I love Van Helsing's bookish adventuerer persona, and the fact that he is so clearly motivated first and formost by kindness. I love Sister Hyde's glamor, and the fact that she was no more evil than her counterpart- she just had a very different agenda. I love Marianne's sweet romanticism, and her (albeit misguided) altruism. Showcase any or all of the above and I'll be happy.
Don Giovanni - Mozart/Da Ponte
This is such a rich work with one of the nastiest villains in all of opera, and I feel like it often gets undercut when productions try to soften or excuse Giovanni's conduct. Give me horror, give me suspense, give me AUs, give me Anna and Ottavio managing to get their revenge on Giovanni...give me all of those or none of those, but don't give me an Anna who was lying about what happened to her. If Giovanni offers no justifications for his crimes, neither should we, and there's already so much to work with.