I have used some plugins that change some of the icons used in the toolbar (I currently have Menu Icons Plus), but I would like to add custom icons (specifically to the back button), and possibly even make my own theme eventually. Where can I find information on that? I've extracted the omni.ja files, are all the PNGs in there? When I eventually finish the theme, how do I install it without overwriting the defaults? I can't find any documentation on this.