RE: What does one do with assets held on a shutdown game?

That would be a good idea. A personal NFT museum that could be open for viewing. The 'metaverse' space Decentraland is a good example of people showing off their NFTs in a gallery to anybody who ventures in.

There are other methods too like generating a space or creating a page to 'show off' my ventures in NFT applications but it would probably appear similar to an old sports card shop.