Lobby CSS customization
Theming in FAFLobby 0.5+ works as follows: Everything you see in folder _res can be themed. Simply create a folder _themes/MyTheme and put only the files you wish changed in there. You can then choose the theme from the Settings menu in the Lobby.
Yes, you can even change the entire UI layout, as long as all the types and names remain the same.
In the early stages of 0.5.x, ui files will change a bit now and then, and sometimes even a lot. So themes will need frequent small and sometimes big adjustments - sorry.
There will be an opportunity to mod the colors and formatting of the chat as well in one of the next updates.
Everyone is welcome to make themes for themselves or share them with others. The only requirement is to make the theme yourself, not just post a mockup and hope it will be created for you.
Additional resources will also be added frequently (mostly banners, watermarks and icons) and they won't break your mod, but you may want to put in modded versions of such new files as needed.
If your theme is particularly awesome, it might even get packaged with the lobby installer if you agree.
Resources for Theming: Supported HTML subset by Qt : http://developer.qt.nokia.com/doc/qt-4.8/richtext-html-subset.html
How to Customize Qt Widgets : http://developer.qt.nokia.com/doc/qt-4.8/stylesheet-examples.html#customizing-specific-widgets
Finished themes can be found in this forum thread.