Skin making using Blender's texture paint.

One of the most recent hobbies I picked up over the summer was making skins for a game called "Attack On Titan Tribute Game" by Fenglee.

A Modified Sasha

I'd take the texture map from the source files and edit it in gimp. However if it's your first time working with a texture map it can get a bit confusing. Knowing what goes where, and how the texture warps on the 3d object.

I'm going to teach you how you can directly paint onto the 3d model using a free program called Blender. 

You can use this method to add in preliminary details and refine it later in Gimp or Photoshop. You can use this method for any 3d models you find/create.