Fixed Unity/Gnome3 and switched to Curl

When I updated to add a config/download dir, I didn't update where Unity/Gnome3 grabbed the background from, so they didn't work. Ugh.

In testing, I also found that wget isn't including by default with Fedora, but curl is (as well as just about everywhere), so I switched to using that to grab the images. Hope everything works now. :)