Google Earth, WorldWide Telescope, Universe Sandbox, AstroGrav, GravitySimulator, NeutronStar, you're an astrofreak!
Google SketchUp...
That's great, I love drawing 3D in it aswell.
Oh, wait, we were talking about the background?...
It looks fine, but a little bit too colorless and without so many features of it in my opinion. Yes, the planets and the Sun and the eclipsed pics plus the Moon look fine, but I prefer a full image of a galaxy or something like das.
My background is the Whirlpool Galaxy, my favorite!
Consider it.