The new GNOME shipped with fedora 20 has the awesome new ability to set
different backgrounds for both the lock screen/shield and the normal
regular desktop background.
Currently in f20 alpha TC4, we set the old f19 default background for
the desktop, and a completely different pink, fan style design for the
lock screen. IMHO, the defaults should behave the same as the f19,
setting the default background for both.