Install lubuntu-artwork-18-04 by entering the following commands in the terminal:
sudo apt update sudo apt install lubuntu-artwork-18-04
Description:
artwork for Lubuntu - 18.04 version
Artwork for Lubuntu, contained the wallpaper and others specific images and logos. . This package contains theme of Lubuntu 18.04.
Homepage: https://launchpad.net/~lubuntu-desktop
Version: 0.71
Section: universe/x11