If you are using LXC virtualization, we now have images for CentOS 7, CentOS 6, Ubuntu 16 and Debian 8, available for download. Just login to Cloudmin and go to Cloudmin Settings -> New System Images, search for "LXC" and download the ones that you want. These images are all base OS only - they don't include Webmin or Virtualmin.

Please note that a 64-bit host system is needed to run these images. Similar 32-bit images may be provided in future if there is enough demand.