They have the same textures, but differ from the normal ones in smaller sizes.
Several special Axolotl variants are available:
Put a Name Tag or Spawn Egg on an Anvil.
Rename it like this: "Ender." Make sure the first letter of the name is uppercase, be aware of the spaces, and don't include the quotes ("").
Use the nametag on a Baby or Adult Axolotl and finish!
Comparison of Axolotl sizes with a Crafting Table:
Crocodile and an Ender axolotl variants: