Superpaper is an advanced multi monitor wallpaper manager for Linux and Windows operating systems, with partial and untested support for Mac OS X.
Supported Linux desktop environments / window managers are:
BSPWM Budgie Cinnamon Gnome i3 (via feh) KDE* LXDE Mate Pantheon XFCE*
and additionally there is support for
feh supplying a custom command to set the wallpaper
if support for your system of choice is not built-in.
*KDE and XFCE work most reliably with monitors in a single horizontal row: some configurations with 3 or more displays in a complex/non-row setup can have issues with spanning.
I think some of you kids might be interested in this..