Credits:
cambiogris - Original creator
uberhen - Tileable background (still uses cg's sky), conversion to B26
I'm no artist, so you'll have to forgive the slight seam in the background and the positioned image dithering.
If you would rather play in 640x480, use cambiogris' original background, which I've also kept in the RTE. You just need to rename the .bmps.