$ for f in $(find tileset | grep "\.png"); do if ! grep -qr "${f}" ./; then echo "${f}" >> unused_tilesets.txt; fi; done

tileset/furniture/other/comp_things.png
tileset/furniture/other/tool_rack.png
tileset/ground/dirt_mounds_2.png
tileset/ground/sand.png
tileset/plant/tree/spruce_xmas6.png
tileset/plant/tree/trees_1.png
tileset/plant/flower/leafy_daisy_yellow.png
tileset/plant/flower/small_purple_white.png
tileset/plant/flower/leafy_daisy_blue.png
tileset/plant/flower/leafy_daisy_white.png
tileset/ground/indoor/stonefloor_corners.png
tileset/ground/rock/amethysts.png
tileset/ground/green.png
tileset/ground/cobblestone_paving.png
tileset/building/decoration/bricked_feature.png
tileset/building/entrance/ornamental_border.png
tileset/building/entrance/blue_green_detail.png
tileset/building/entrance/grey_detail.png
tileset/building/entrance/grey_wide.png
tileset/building/door/doorway_top_s.png
tileset/building/wall/int_wall_bricks_tan.png
tileset/building/hut.png
tileset/building/beach_hut.png
tileset/building/fire_tower.png
tileset/building/witch_hut.png
tileset/building/ice_tower.png
tileset/building/life_tower.png
tileset/building/beach_hut_pink.png
tileset/item/pot/iron_pot.png
tileset/item/gothic/headstone_6.png
tileset/item/sign.png
tileset/item/chapter.png
tileset/logic/creature/dwarf_deep.png
tileset/logic/npc/animal.png
tileset/logic/forces.png
tileset/object/exercise_wheel.png
tileset/object/rock/rocks.png
tileset/object/rock/rock_face.png
tileset/object/boardwalk_with_stairs.png
tileset/terrain/wall/stone.png
tileset/terrain/wall/brick_wall.png
