Its very easy. All you need is Microsoft Paint and WinRar in PC or PaintCAD and MiniCommander in Mobile.
PaintCAD.jar (271.41 KB)
MiniCommander.jar (230.28 KB)
1. Right-click on any of the skin and save it as s.png on your desktop. Then, open it on Microsoft paint/PaintCAD.
2. Edit the image and change anything you want except the resolution of the image.
3. Save the changes you made on s.png and close paint.
4. Open operamini 4.2 with WinRAR and drag s.png on it.
5. Click Ok and close WinRAR.
6. Finally, install your modified operamini.jar on your phone or use microemulator on your computer to test your work.
In mobile, you can use PaintCAD to Edit the image and MiniCommander to save it.