How do I change wallpapers via command line in Kubuntu 12.04 (KDE 4.9), with the same effect as right-clicking the desktop and pressing "Next Wallpaper"? Maybe through using Dbus or something?

Code:
alex@kubuntu:~$ plasma-desktop --version
Qt: 4.8.2
KDE Development Platform: 4.9.1
Plasma Desktop Shell: 0.4