I recently Installed 12.10 version and I loved it! But the there's something weird with Wallpapers. As long as I use a wallpaper from the /usr/share/backgrounds folder (I use the "appearance" dialog box), this wallpapers appears also on my welcome (login) screen. But when I try to use a wallpaper from my pictures folder (again using the "+" button from the appearance dialog box), my login screen has the standard ubuntu 12.10 wallpaper. Is there anything I can do to fix this?

Thanks in advance!