From a clean 13.04 Ubuntu install, just
Don't install ubuntu-gnome-desktop or the staging ppa as described in that article. Reboot and log into gnome shell. Run tweak took and disable "have file manager manage the desktop". You should get your desktop background back then.
sudo add-apt-repository ppa:gnome3-team/gnome3
sudo apt-get update
sudo apt-get dist-upgrade
sudo apt-get install gnome-shell gnome-tweak-tool
You don't really want icons and stuff on your desktop anyhow, as I argued from here.
Actually I suspect you may even be able to use the file manager for the desktop if you install ubuntu-gnome-desktop but I have not tried it because I don't want the file manager, and also I much prefer the default Ubuntu Ambiance theme and font etc for gnome shell in preference to the standard gnome theme and fonts.