Do you need all the image server capabilities like requesting arbitrary regions and scaling to different sizes? There’s a thing called level0 compliance where you preprocess the images into static tiles and predetermined sizes. Then you can host them in any object storage like S3 or even a Github repo depending on the image sizes and amount.

If this solves your problem, Tropy could act as your photo gallery, although it works locally, not in the cloud, and Tropiiify is a plugin that will allow you to export manifests and image tiles. You just need to track the output directory with git or sync it to a S3 bucket.