Textures with resolutions lower than 16 pixels don't get rendered properly. It only appears on the lower left corner of a block. Same thing with all items.

What I expected to happen was for the texture to display on the whole block, but it just displayed on the lower left corner of a block. All items in the inventory also display the same way, except it is on the upper right side. The empty areas were 0% opaque.

To reproduce this:
1, load any texture pack lower than 16px
2, stare at the textures in Minecraft