The new Theme Banners improvements are now live, more about this on the Noticeboard: Bigger, Better Banners.

In short - all themes now have configurable big banner images. Once enabled at a theme level you can optionally then set a different banner per-Application, or per Page in the CMS.

The Bootstrap theme has also gained some more placement options - e.g., so you can have the navbar above or below the banner.

Enjoy!

Joe