This allows your lightweight theme to spread onto about:newtab, about:home, about:addons, about:sessionrestore, and file: url pages in Firefox. Only tested on Linux so far.
* Firefox really doesn't like to give up images in its cache. I try clearing it, but it doesn't seem to always work. i.e. If you change themes often, it may take a little time for everything to sync up.
* Doesn't seem to clean up after itself right yet. Everything disables, but the theme css file likes to linger
* The color analyzer I'm using to find something to blend with doesn't ever work. It always falls back to the accent color, which looks nice sometimes, and not nice others.