Customize web interface appearance?

[NetwarSystem]

I've been using ArangoDB for a couple years but am only starting to do stuff with Docker in the last month or so. I recall early on that I found a way to change the logo on the web interface page so that I had a visual clue as to if I'm touching R&D instance or production.

This really should be part of a configuration dialog rather than digging around in CSS and stuff trying to figure out how to make systems visually distinct.