The usual seed of the day (which you can play only once) and seed of the week (which you can play multiple times) on a scoreboard to challenge your friends.
I also like the idea of if you beat a game, you can donate a card to a friend. Then in one of his games, when that joker pops up in his shop, it's free, or polychrome, etc. Maaaybe a non-blueprint/non-brainstorm card. lol
#Asynchronous multiplayer ideas
karmic cloak
pure wraith
Don’t think the card donation thing would work well with balatro’s RNG system, and could lead to weird balancing, but I would really appreciate a daily seed