gnome-settings-daemon is not responsible for the login window theme. This app sets the user's preferences for GNOME after that user has logged into their desktop.
If you're referring to the login screen (the screen where you enter your username and password), on Squeeze it's called gdm3 (gnome display manager) which is actually a GNOME session that's run as the user 'gdm'.
Unfortunately, this screen is not themable anymore, but is in fact highly customizable.
If this is the screen you're referring to, please check to this thread: