thisguyisjoe

I'd guess your renderer isn't making use of the metadata you've used to store the block's direction. I'd look in TileEntityChestRenderer and see what I could do to make the renderer for your Iron Chest the same.

How will the tile entity itself be able differentiate which type of block it is? I have a multiblock mod of my own which uses metadata to determine the appropriate tile entity and, if I'm not mistaken, Minecraft uses metadata to determine texturing for anvils and ovens. From my own experience, the performance hit of using a tile entity over a block isn't that large. If you're curious to test it, try replacing dirt or something with brewing stands or another tile entity in a test world.