As a starter, look for a "dumb" service that doesn't treat photos differently from any other type of binary blob. No thumbnails. No grouping by date or location

As a starter, look for a "dumb" service that doesn't treat photos differently from any other type of binary blob. No thumbnails. No grouping by date or location. No tagging other people. The storage service should only concern itself with safekeeping the binaries you upload, not analyzing and processing them. Use your own machine to do the latter.