Given that for images one does not need to do random I/O, any kind of object storage system will do much better than NFS or any other kind of network filesystem

Given that for images one does not need to do random I/O, any kind of object storage system will do much better than NFS or any other kind of network filesystem with POSIX semantics guarantees. And no, in real world, you don't use what works, you come up with a design other people won't have to painfully maintain for the next 5 years.