I have various tilesets in a single pack called Multi Platformer Tileset, using PICO-8 palette for it. And currently there are more tilesets incoming in the future. Some of them are still in paper.
I currently revamped the first environment, Grassland. As leaving the old one to rust fells bad, I decided to give the old one for free, so here it is.
It have a terrain tileset, parallax scrolling backgrounds and additional assets (with a few animations). All this pack have 106 assets. Of course, in .png format.