In Ubuntu 13.04 (Unity) from the right click menu (on the picture file) when "set as Wallpaper" is selected wallpaper is changed however source file is copied (not moved) into ~/Pictures/Wallpapers which btw is also created. Original file is still located in original location (for example on the desktop) - so, file is really duplicated.
If source file is already located inside ~/Picutres/Wallpapers folder, file is also duplicated: new file has "(copy)" added to his name (ie.: name_of_file (copy).jpg).
Workaround for this is to open file in Eye of GNOME Image Viewer and choose set as wallpaper from the right click menu which works fine.
ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: nautilus 1:3.6.3-0ubuntu16
ProcVersionSignature: Ubuntu 3.8.0-20.31-generic 3.8.11
Uname: Linux 3.8.0-20-generic x86_64
ApportVersion: 2.9.2-0ubuntu8
Architecture: amd64
Date: Sat May 18 19:41:01 2013
GsettingsChanges: b'org.gnome.nautilus.window-state' b'geometry' b"'800x550+49+24'"
InstallationDate: Installed on 2013-04-26 (22 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
MarkForUpload: True
SourcePackage: nautilus
UpgradeStatus: No upgrade log present (probably fresh install)
Status changed to 'Confirmed' because the bug affects multiple users.