Well, first get a transparent box. Scale it 256x256
Next, Color the decal, draw whatever you want!
Then, save it as what you drew. And make a folder called: Decal_(whatever the name is) Put your face in that folder!
Next, make ANOTHER folder inside the Decal_ folder and call it "thumbs" (without ")
Last, copy your face and paste it in "thumbs" go into the "thumbs" folder and resize your face to 64x64!
And then... YOUR DONE! Hope this helped!