Minecraft wiki entry for Glazed_terracotta_patterns, associated text: Most terracotta blocks have a "centerpiece" in one of the corners. This could be anything that stands out from the rest of the block, such as the flower petals on the orange and white terracotta, the rings on the green terracotta, and the creeper face on the cyan terracotta. Generally, the prettiest 2x2 patterns come from either putting these "centerpieces" on the inside, thus creating a flower in the middle for orange and white terracotta, or putting the "centerpieces" on the outside corners.