Ubuntu 12.04 Unity greeter had introduced the selected user dynamic wallpaper which allowed, when selecting a user from the available users list in the login screen, the wallpaper to change to reflect the selected user's desktop wallpaper.
Apparently that feature has been disabled by default since Ubuntu 12.10.
How do I enable that feature in Ubuntu 13.04?
/etc/lightdm/unity-greeter.conf
(from @Hernantz's answer to the same question)?