Looks very interesting!

But I can’t find an answer anywhere to the most important thing in my opinion — how providers supposed to compete?

Lets say, provider receives new NIP-90 event - should it send some “portfolio” (probably adjusted to request) back and wait for approval? Should it generate the image for free (maybe with a watermark) beforehand and wait for a payment to provide full image?

Also, is it supposed users and providers must be connected to the same relays qt this point? Did you think how to approach this?