Character skin has to be a 64 by 32 PNG file. No longer true: Reference skin can be downloaded from http://minecraft.net/skin/. You can use your Minecraft username: http://minecraft.net/skin/robothacker.png Replace "robothacker" (my Minecraft username) with your Minecraft username (or someone else's Minecraft username that has a cool skin.) The usernames are case sensitive, to get Notch's you have to use "Notch" with the uppercase "N".
URL character skin:
OR:
Upload character skin:
Hat style: Sides attach to top Sides attach to face Do not include hat
Head style: Sides attach to top Sides attach to face