This may be of interest to users of Hydrus: I finally got off my ass and wrote a replacement for the janky pile of garbage slideshow program I used to use to view my export folders on my secondary monitors.
https://github.com/VerstandInvictus/DevilScreens
This was coded because I needed something to cycle through my export folders, but it should work for any collection of images whether or not they came from Hydrus. If you have your export folder filenames set up to include "namespace", then that namespace is displayed as a label at the bottom of each image.
Still sort of rough and under heavy development, but totally usable if you're ok with INI files. Controllable (next/prev/pause/play) and has an "open file" button. Please do submit feature requests/bug reports/pulls/whatever on Git or in this thread.