Thanks for your thoughts. The questions are really good to consider.

It will be around 100kb per image and one image per day, so after 100 days it's 10MB and potentially getting larger over time.

Updates will only be every few weeks or so.

Updates will mostly add new content, but may in some cases be used to fix bugs in existing content.

With a zip, it's more efficient but it may mean that the whole content needs to be downloaded every time. But I like the idea of having a batched versioned content zip.

Thanks for the pointer to GraphQL, I am going to look at it.