$ sudo apt-get update
$ sudo apt-get install edubuntu-wallpapers 

edubuntu-wallpapers is installed in your system.

Make ensure the edubuntu-wallpapers package were installed using the commands given below,

$ sudo dpkg-query -l | grep edubuntu-wallpapers *

You will get with edubuntu-wallpapers package name, version, architecture and description in a table

edubuntu-wallpapers package basic information: