With the release of 1.6.0 you can now use getResource for recursive, nested menus in MODX, instead of the Wayfinder snippet.
The MODX Resource object has a secret-not-secret field, "properties" in which you can store a JSON object with any kind of data you like. However, there's no UI with which to edit that field. Here's some code to help you utilize it.
Selected articles from the official MODX Blog, by the author of this blog.
This modification of the cbGetFieldContent Snippet allows you to specify a comma-separated list of fields from which to try to fetch content, rather than being restricted to one field.
Update on MODX Revolution 2.2 site build: schema.org implementations.
How to setup MODX for client preview permissions level "Anyone With Link Can View".
If powerful tagging of images is the most important feature/requirement of your gallery, then this tutorial demonstrates a performant way to achieve it in MODX CMS.
A MODX Snippet for rapid prototyping.