I remember learning about IIIE (triple-I-efe) years ago while working with a computer vision researcher that used it to serve images generated with Jenkins pipelines.

Glad to see the project of server I used is still running well. The maintainer was a really nice person to work with too: https://cantaloupe-project.github.io/

It helped me that I was already familiar with some OGC & GIS tiling technologies, as what IIIF is doing is not too different. The image processing layer is different though, as you can zoom in, out, rotate, scale, etc..

There were several JavaScript clients, the one I used was one adopted by a museum, but I cannot recall the name now.