replace header background image

this is a cleanup of https://github.com/xbmc/xbmc/pull/3940

it replaces the header background texture in a number of places, to improve readability.

for @uNiversal


![readability](https://f.cloud.github.com/assets/687265/1847648/c48e3a82-765d-11e3-865c-ef9ae594258f.jpg)