This image mimics a Lubuntu Desktop by installing the packages ubuntu-minimal, ubuntu-standard and lubuntu-desktop on top of the latest Ubuntu image, and enabling the multiverse and backports repositories by default. The Dockerfile can be seen on MicroBadger.
The lubuntu:latest tag points to the latest LTS release, which is currently lubuntu:16:04, but non-LTS images are also available, for example lubuntu:17:10.
WARNING: If what you are looking for is a lightweight image, either use the official ubuntu or alpine images. This image can reach 1 GB in size, and is used for testing my Ansible provisioning in a CI.