Which component controls the "universal" app background On Gingerbread, which component(like SystemUI.apk) controls the universal background?

To better explain myself, here is a screenshot



I'm referring to the blue background with the gradients
This is actually a system theme. Any app that is written to run under the theme of the device (unless you're root your devices theme is not changeable) will grab backgrounds, etc from that theme. It is like how most apps on the Nexus devices run with the Holo theme.

Edit: Just to clarify I am saying this is not an app, it is just a theme.