You would at least inspect the file art/skins/elves.zip in your PlaneShift installation and guess which element may have which meaning.
Then you would possibly alter the graphics and test now and then what happens when setting up your own ZIP file in the folder art/skins, selecting it in PSLaunch, and running the game with it.
Note that the GUI supports alpha transparency in PNGs, so use an image editor which is able to handle gradual transparency.
Furthermore, there are still some images in art/materials.zip related to the appearance of the skin, which you may not be able to publish as easily as in a single ZIP archive of your own skin.