I just installed this wonderful plugin. It reminds me of the Stash Reels plugin, except your plugin can display images and markers, can manipulate metadata (e.g. tags), and has a query feature. 
-
Possible rating bug. My Stash ratings setup is vanilla. Rating system type = stars, rating star precision = full. However, I noticed StashGifs is displaying markers using the 10-star system.
-
Suggestions
a. UX consistency with Stash. This is more philosophical than anything, and probably not a big deal to many users. But the plugin changes the Stash colour/font schema which breaks consistency. Consider adding a settings toggle to disable any styling that departs from stock Stash (colors, font, etc).
b.
Auto-fit content to viewport. Consider adding an option in the settings to toggle auto-fitting of content to the viewport. Many portrait oriented items get displayed off the viewport. Never mind if that behavior is an intentional design decision.