I'm super glad to see that there are so many people interested in this (at least based on how many have joined so far). I figured it was about time we had a Tarot jam. It's a very rich vein to draw upon. Anyway, it's a two month long game jam, and there's no rule against starting early, so you have plenty of time to brainstorm, and plenty of time to change your mind.
The Tarot is a very interesting thing to explore from a game design angle. I feel like it's steeped in all sorts of occult lore these days, but it was originally invented for the purpose of playing games, and I know I'm finding it to be a cool platform to work with. My own current concept (although this may change) is a tabletop roleplaying/storytelling game that uses the Tarot to generate the game world and to resolve in-game actions/disputes, but one could come at it from many different directions. Definitely doesn't have to be a game that directly uses Tarot cards as part of its mechanics.
Anyway, if you do decide to make something for this, I'll be excited to hear about how things are going.