following Textures created by Fernando Zapata (CC BY-SA 3.0):
  door_wood.png
  door_wood_a.png
  door_wood_a_r.png
  door_wood_b.png
  door_wood_b_r.png

following Textures created by BlockMen (WTFPL):
  door_trapdoor.png

following textures created by sofar (CC-BY-SA-3.0)
  doors_trapdoor_steel.png
  doors_trapdoor_steel_side.png
  door_trapdoor_side.png