I was playing around with the custom superflat world thing. I was going up by 10s to just see what blocks would come up. I hit 130, the ID for Ender Chest.

It rendered REALLY weird.

When I first discovered this, my minecraft was modded. I tested it on a fresh Minecraft 1.5.1 jar to make sure it was a vanilla bug, and it also happened there.

I have not tested this before 1.5.1, but I wouldn't be surprised if it also affected 1.5 too.

I was going to say it might be due to the unstitched textures, but I almost forgot that enderchests and chests do not use the same type of textures as other blocks.

How to test:
1. Click Singleplayer
2. Click Create New World...
3. Click More World Options...
4. Change World Type to superflat
5. Click Customize
6. Go to Presets
7. Copy and paste this in the preset box: 2;130 (Or use any code with block id 130)

EDIT: In 1.8 snapshots, you can use 3;minecraft:chest or 3;minecraft:ender_chest