What you need to do is line up the skin correctly. In this case, keep scrolling until the skull is all the way to the left (look at the green lines at the top of the texture, and you'll see it's "off". Next, use the down arrow in the lower-right corner of your picture until the green lines at the top are gone and the texture is at the top. Copy the offset= number (in the red section below file size = 976,410). That's what you will use in Muaskinner. Open SkinnerGUI and choose 'CFG edit'. Load 2103 punisher.igb, then in the 512x512 section put your offset. Hit 'add' then accept. Now when you go to 'view' you should be able to see the skin.
You will notice there is a smaller texture below. That is called a mipmap and is used when the character is farther from the screen. Using the same process, change the WIDTH section to 256 and repeat the same steps, recording the new offset. Then in SkinnerGUI open 'CFG edit' again, load 2103 punisher (even if it is already loaded) and put that offset in the 256x256 section. Lastly open your texture and save it as 256x256, then import. You may need to repeat the process for 128x128, 64x64 and 32x32 textures.