They can take the site down but he NFTs can't be removed at this point
If this wasn't a joke, it would make an interesting demonstration of how the value is purely the current social consensus: a receipt is of dubious value in any case but it would be especially unlikely to attract buyers when the target URL has been DMCAed.
The jpeg could be on IPFS, bittorrent, freenet, whatever. Look it up by hash and verify the hash after getting it. If takedowns are a problem, use the more censorship-resistant options.
If something is taken down for legal reasons, you're left with intersection of hosts who are in legal jurisdictions where they can blow off those complaints, don't have their IPs blocked, and are willing to host it for whatever you want to pay.
That's not impossible but it's far from the solved problem NFT salespeople present it as, increasing in difficulty with the value of the content.