For the cell image, I cut the image into map tile layers by scripting imagemagick. These tiles are served from my server.

For the overlaid areas I use geojson data, which I create and update with a geojson editor I am working on. For actual maps I have https://qquiz.com/makegeo/e.html . An example of non-map images, https://qquiz.com/boat1/e.html . The editor lacks instructions still, but is pretty easy to use.