Tileset of the game zwischenwelt ( http://zwischenwelt.org/ ). The game itself is inactive for several years now (although it might still be online). 

People that contributed to this set (alphabetically): darian, elara, ghoulsblade, hagish (me), isha

It contains a lot of single images and prepared spritesheets + json meta files (texturepacker). There is also a small tiled example map.