Firefox 29, scheduled for the end of April, includes significant design and customization improvements that you can read more about here. You can also experience the new design, nicknamed “Australis”, for yourself on the Aurora channel now. We’ve blogged about how the toolbar, menu, and button changes will affect add-ons, but we also wanted to mention how the changes will affect lightweight themes.
In Firefox 29, the amount of header image shown remains nearly the same, but it now stands out more because the area is less cluttered. You’ll notice that the foreground tab, URL bar, and toolbar are emphasized by a sheer overlay. This makes it easier to distinguish your active tab from non-active tabs, and it also happens to make themes look gorgeous.
Since the add-on bar is going away, you will no longer see a footer image when you install a theme, unless you are using an extension that modifies your browser to include a bar on the bottom (for example, S3. Download Statusbar). A bug has been filed to make footer images optional when uploading a new theme, and in the future the option may go away altogether.
We hope you install Aurora and give it a try!