Make a game that uses Tarrot cards as a resolution/improv mechanic. - Have you ever played Sine Requie or Alba di chtulu? (I do not even know if they get translated) they use them and they are very interesting horror games
I love resolution mechanics like City of Mist or Spell (using Scrabble for magic) with almost unlimited freedom based on the words you invoke. Maybe something where you print out lyrics and need to use lines to do actions, never using the same line twice. - not a fan of City of Mist but I really like free-word-based character sheets, like Not The End or Fate.
Sadly I have almost finished my submission for this jam but how is going with Timetraveler's Guide to Paradoxes? next week I can help with it if you need. Seems interesting