I have been using gnome-shell for a few months. I was able to configure it using "tweak tool" and "background". Now I've just migrated to Unity, but "Change Desktop Background" (comes from right-click on desktop) launches "System Settings". I'm not able to swap desktop wallpaper or change launcher icons' size, etc. As you can see from this picture, the "Appearance" icon has been removed from "System Settings". What's happened to my Ubuntu?
My OS: Ubuntu 12.10; Unity + gnome-shell; latest updates