This presentation demonstrates how a Reveal.js plugin can be added.
The plugin is called revealjs-simple-gallery.
It can make any slide an image gallery. Here are a few examples.
See the revealjs-simple-gallery GitHub repo to learn about more customization options.
These were the steps to use this plugin for this reveal-hugo presentation.
plugins field in the front matter
head.html partial inside of
head.html, add a stylesheet link tag that loads the plugin CSS