login background

If you're talking about the "Foam" (or whatever 'xactly it's called) picture that's shown in the background in 10.1 ...yes. If you're talking about the basic blue in 10.0.x ...no.

If you're on 10.1, just move /Library/Desktop Pictures/Aqua Blue.jpg somewhere else, and rename whichever you want to be displayed to Aqua Blue.jpg. Whenever you next login, you'll see the picture you selected. :)
I think apple should make the login panel skinnable :p
It would be cool ;)

Do PB login panels word in 10.1 ?
Heh...I posted a pic of my login panel in the thread Post your OSX Desktop Pics!!! (or something liek that) in the General Discussions forum...check it out. It's somehwere close to skinnable...;)