Must have been a temporary launchpad bug, nautilus bugs https://launchpad.net/distros/ubuntu/+source/nautilus/+bugs were all shown as unconfirmed and unknown. Guess it's been fixed. Sorry for the bother.
-- several backgrounds for each virtual desktop https://launchpad.net/bugs/18397 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
