Thanks!
There are quite a few mods on lexaloffle (the main sorta website for pico8) https://www.lexaloffle.com/bbs/?cat=7&carts_tab=1&#sub=2&mode=carts&search=Celeste, and there are whole collections and jams of mods like https://evergreengames.github.io/cchristmas/ and https://itch.io/jam/ccmamj. many of these have ridiculously high polish and quality.