I've been looking throughout the internet for an hour or two and the effort has been fruitless. Is it even possible now that the skin editor site is shut down? I already have one custom skin installed, but I can't find it's file in my PSP as I don't even know what's its extension! It's sad, really, I found some really nice skins and their copies of the editor images. It would be a shame not to be able to use those.