How to create icons
From Craftland Minecraft Aether Server
This is how to create an icon with blender. You'll need blender. Once you downloaded it, download [this http://dl.dropbox.com/u/5401956/Block.blend]. This is a pre-made model. After, follow this video. You might need to move the texture position by pressing G or resize it with S. If you want to resize it only on the X dimension, press S then press X. Same for Y.