Customizable Player Models
Create a custom avatar using the built-in editor.
The models are stored in unused space on your Minecraft Skin, or as a Gist on GitHub.
Upload the exported image file as your skin to load the custom model.
Parts of the normal player model can be hidden or moved around.
You can even make parts of your skin “glow” like a glow squid.
Plugin for Bukkit/Spigot servers for changing skins ingame (not required): https://github.com/tom5454/CustomPlayerModels/releases