I changed the login background in Snow Leopard. Each time I start up the computer, I see my nice new login background, but after I log in, I get the same old Aurora image for about a second before the regular finder wallpaper replaces it.
My finder wallpaper is stored on an external disk. I think that the Aurora wallpaper is shown by default because it takes a second for the system to find the wallpaper on the external drive.
It seems likely that there is a preference for a default wallpaper if Snow Leopard can't find the wallpaper used during the last session.
Does anyone know where this preference is stored?