Create a backdrop for the new navigational floatitem as can be seen in this mockup:

http://devel-home.kde.org/~tackat/navimockup.png

The graphics assets are here:

devel-home.kde.org/~tackat/navigational_backdrop.tar.gz

All graphics are meant to be concatenated at runtime and are supposed to be placed as a background image of the whole widget.

The center part is supposed to get scaled vertically so that it matches the slider height (unmodified for the default height though).

The result should pixel perfectly match the mockup.