I am impressed with the map story template. I am hoping I can use the template to display many hundreds of geo tagged images. I have a concern that the story template is not really appropriate. Is it worth pursuing or should I look elsewhere. For example there is dedicated software for mosiacing hundreds of images together.
Map Tour and Shortlist are by default limited to 100 images (per app for Map Tour ; per tab for Shortlist). We provide icon set to go up to 200 hundred on Github. First thing for you would be to extend that icon set or stop numbering them (Map Tour has that option through configuration in the downloadable version).
With 1000 thousand images, apps should still run smoothly on modern desktop browser but they will become quite slow on mobile device and older desktop browser. Make sure sure to aggressively optimize the weight of thumbnails and thumbnails, this can change everything.
Besides the technical aspect, we don't recommend having that much point with Map Tour and Shortlist because it can makes your story difficult to browse. After that it of course depend on your story :). We haven't heard about user doing very large Map Tour but I think it's worth trying and I would be glad to have your feedback.
Uploading image one by one in Map Tour builder can be a long process that's why you can import from popular online service that will do the thumbnail generation and have very solid multi-images upload. We also have a lot of user using desktop software to create thumbnail, putting them on Dropbox and reference them in a CSV.
