[Shotwell] Shotwell, early draft

[Joshua Gentry]

I've only been lurking on the mailing list a few days, I'd say keep the
background slider.  I've personally never changed it, the default color
is fine for me, but I'm always in favor of customizations that are easy
to explain and do not confuse the user.  I don't think the slider would
confuse people especially since you can see the changes immediately
behind the dialog box.  Although a "default" button might be nice for
it, but I don't see that as critical either.