I just fired the apple aqua theme onto mine and it worked fine. Thought I'm not afraid to brick my gp2x I'm sure it would just skin everything and use the default on what it can't. Thought I have no freaking clue so maybe ignore me.
There is one 2.0 compatible skin so far: Candy skin. You could download that and use it as your template. Their are some extra screens and icons, mainly I find the skins from earlier firmwares obscure the icon in the top left corner when in the file explorer, the one that shows which editting feature you are currently using.