Jeje, fair questions, I have some idea of some of your concerns:
1.- Priced based on how many times it has been bought and sold, meaning that only fairly famous or succesful NFT's might qualify for loans
2.- Revenue: Put your cat picture on decentraland inside of a digital museum that charges per customer, just like a normal museum, but all using the decentraland token, this is just one possibility for revenue generation, your cat picture can be put on a game and give you royalties based on interactions, etc
3.- Additional Collateral could be set on ETH, similar to what is done on a margin trading platform, where they liquidate your position if in danger of being underfunded.
RE: NFT loans will be huge, imagine paying your mortgage with a jpeg file ...