Yes we have hooks for spreadsheet inserts/updates/deletes and we will be working on the frontend part to make it modularised as mentioned in another comment.
Store images in BLOBs - we aren't against it. But we ran short of time to make that work for all databases.
For file storage : it used local filesystem if no storage app is installed.
You can connect to wide variety of storage services : S3, Minio, BackBlaze, GCS, Azure to name a few. I believe Azure storage isn't tested as we didn't have credits with them :)