Maybe only some images get flagged with the metadata that say that they work with Twitter, and OpenSea pays Twitter a 10% cut of any works-with-Twitter image rights they sell?

If a user has already spent money purchasing an NFT that they want to use as their profile picture, they will almost certainly spend a bit more for proof of ownership.

make it only available to accounts that pay for it. Could work with that crowd. (or make it a paid thing on the seller side, pay to opt an offered series of pieces in). But probably overall not that much money to be had.