Step 1: Resize the Texture
To be sure you'll see the pixels of the final object, you should open the texture in a image editor (The Gimp, for example) and resize the texture of your skin without any interpolation to get an image with dimensions 512x256.
Step 2: Customize the 3D Model
To apply your texture on the 3D model of the minecraft avatar, you can use the tools provided by the service sculpteo .
For this, go to this webpage where you'll find the original 3D model and tools to customize it.
Step 3: Active the Operation "replace Texture"
Among the available operations, choose the "Add an image anywhere on the model " operation.
Step 4: Change the Texture
Now, you can change the texture used by default by uploading your own texture. Then, you precise you want to " replace an existing texture ". The unique texture is then proposed to be replaced and you click on it.
Step 5: Order Your 3D Avatar
Then, you can order your 3D model by specifying the size of the final object.