One of the sites I maintain recently had a server upgrade to Ubuntu 14.04.4, which included a new version of varnish (version 3.05) which required an update to the Varnish configuration. After setting up a new default.vcl file I was monitoring the headers sent and received to make sure that what was supposed to be cached was in fact being cached by Varnish. While testing I discovered that I was not getting any Cache-Control headers from static files like images.
I'm a huge fan of Elon Musk, the world-changing, South African born pioneer of the consumer electric car and space technology company SpaceX, and was pleased to learn that both the Tesla website, and the SpaceX website are built on Drupal. Both are currently Drupal 7 sites with home pages that use beautiful images and videos (in the case of the Tesla site) to provide high visual impact and engagement.