background image location

["Adam Sleight" <adams linearcorp com>]

when various image programs set your background (root window)  exactly where is
that written to?  under /usr/share ...I can't find it for the life of me.

Does Gnome control center store in it a different location.  I'm using sawmill
0.24.  Is it the window manager which stores it in a specific location?

Like Electric Eyes or GQView....where is the image stored which displays the
background?