In the sidebar it would be great to have a Random Garage widget but the ability to select all Garages (which would use all categories) or pick a category and show random garages for that category so the widget could be used on different pages that align with the category.

The widget would display photos from the garages for the configured category.

I like this idea. However, per Invision's setup of blocks, the same blocks (aka widgets) would show on all the categories and with block caching, it would not be really feasible to show these dependent on those pages.