nostr:npub1v0lxxxxutpvrelsksy8cdhgfux9l6a42hsj2qzquu2zk7vc9qnkszrqj49 had an interesting suggestion: File Hosts could create a NIP-94 event (signed by them) when returning the uploaded image URL to a Nostr client.

Then they could easily track the use of their images in the Nostr ecosystem: Receive reports, notifications of use (quote), replies and likes to the image directly, and even direct zaps for hosting the image.