You can install any skin and texture that you find in the gallery for any mob, block or item in minecraft with the resource pack manager.
How to install
Download the Resource Pack Manager.
The installer will guide you through the setup process.
Visit the Nova Skin Gallery
Search for textures using the Mobs, Items and Blocks filter on the left
Find a skin that you like and click top open it
How to download and install the skin
On the skin page, click on the
apply to minecraft button
If you have installed the resource pack manager, you will see a list of skin options to replace.
Click on the one you want to change and you should see a message like this
You don't need to close minecraft to reload the textures, just press
F3 and T ant the same time to update the resource packs.
How to remove one texture
If you don't want a skin anymore and want to return to the default skin you can delete it.
Locate the texture you want to remove, open it and click on the red
delete button on the right.