A little while ago, @psychobunny toyed with a theme called "Rocket", and eventually published it to npm. Not too much happened to it, although he later went on to create the Persona theme, which is now NodeBB's default.
Rocket ended up being a testbed for some experimental features that made it into NodeBB (and some that did not). (e.g. the groups' pages cover photos were originally in the user profiles section of Rocket themes)
A client of ours was interested in using this theme, so we fixed it up, removed the broken bits, polished the rough edges, and re-released it as a child theme of Persona (used to be a child theme of vanilla)!
Install the theme via your ACP.