As would certificates, degrees, legal documents, invoices, ...
Any proof of achievement also falls into the same bucket.
Your wallet will eventually be full of them.
Could be anything - volunteer hours, course certifications, etc.
Tradeable NFTs can also be used for things like concert tickets that should be easily verifiable, difficult to forge, and have a secondary market for trading.
With NFTs, it's primarily about proving that you own something.
That could be art or collectibles...
Or even intellectual property.
And someday, real estate too.
Tokenized real estate will also be fractionalized.