Roy,
I don't see why not since all they consist of are number coordinates and locations of the various window panels for text input / output, characters, etc.
One can examine any of the skin files with a text editor.
Use a graphic peogram to change the border color, design, etc.
Look at a few of the more simple ones to see what's going on and soon you'll realize that they really aren't that involved.
If you plan on using any transparencies be sure to download the MakeTrans program from Zaba's site.
All one needs is a graphics program and a calculator (unless you're good at subtraction in your head).
Maybe a tute is in order.
Good day!