Changing the logo on login screen

[Jeff Gregor]

I'm setting up a couple of old machines as sort of web/email kiosks for 
internal users. I'd like to be able to change the SL logo on the login 
screen to use my organization's logo. I've figured out how to change the 
background image on the login screen, but can't seem to figure out where 
the login panel (gdm-simple-greeter?) is configured. Any help would be 
appreciated! Thanks...