This is maybe a stupid question, but how can I choose my own background image on ubuntu gnome 3?? I click on Settings -> Background -> then I click on the current background preview to change it but I see only the defaults images! No + symbol to add or something. On the 'Pictures' tab there is nothing to select, I get an empty white page? I am running ubuntu gnome 13.04 3.9.6-030906-generic.