I use Notepad++ to edit the .xml files. I make a copy of my file before starting, then open it up and experiment.
So far I have changed colors, changed start and end locations of objects, changed transparancies, and changed objects to visible or not visible to build up the screen changes I wanted. if you have dual screens, remember to change the screen2 file the same as the screen file so both screens look the same.
The biggest changes come from making all new buttons to match my theme, and saving them with the name of the original button, and changing the background pictures.
You can use animated icons if you want, I just have the logo animated on my current Resident Evil theme.
I save all my files under the skin folders in my own skin folder and use that skin in driveline settings.