Some more free tile sets I’ve been working on over the months. They are tilesable 8x8 and 16x16 and are 128x128 canvases. Different genres. Maybe they can help you prototype games. Public domain as well so feel free to build on them however you want.
The lighter stone, the one with the ladder in between is the walls. The top edge, and bottom edge of the ladder is the floor, two colours, black and grey, with sort of merge in with the green grass.