Use a black background
Make a 1 pixel large black pixel, or a transparent pixel from your computer.
Copy it to your phone.
Use it as the background for the Super AMOLED screen.
AMOLED screens don't use battery for black pixels, and the deep black on the Nexus S just looks amazing when you can't really tell where the screen ends.
Plus live wallpapers sucks because it seems to lag up the phone.
I also went to display settings and changed animations into some animations as all animations seems to show some jittery effect when opening apps, which was unpleasant. some animations still shows the screen off effect, so that's cool.