Note: I did NOT make these, simply found them on Digg and thought they should be shared on a proper website for such a thing. Thanks.
Note: Screenshot is of the original version, without rounded corners or the Feisty edit.
1. Extract the contents of into /usr/share/gnome-screensaver.
2. Run ‘gconftool-2 -s - -type=string /apps/gnome-screensaver/lock_dialog_theme human’
Reverting back to the default:
1. Run ‘gconftool-2 -s - -type=string /apps/gnome-screensaver/lock_dialog_theme default’