Changing background in screensaver login

[Magnus Therning <magnus therning org>]

The background behind the login dialogue for the screensaver doesn't
fit with the rest of my theme, but I haven't found any way to change
it.  How can I change it?

/M

-- 
Magnus Therning                        (OpenPGP: 0xAB4DFBA4)
magnus＠therning．org          Jabber: magnus＠therning．org
http://therning.org/magnus         identi.ca|twitter: magthe