Minecraft wiki entry for Animation_placeholder_texture, associated text: Due to the first terrain.png in Pocket Edition being based off of the terrain.png from Beta 1.3, the nether portal texture placeholder from said version is there by default. However, due to the absence of nether portals in this version, it remained unused until its removal in v0.8.0 alpha build 2. A second placeholder texture was added when nether portals were actually added in v0.12.1 alpha build 1.