Only since January this year (2023) is it possible to incribe text and images directly to the bitcoin blockchain. I wrote about it in earlier posts.
Since then marketplaces have been build for Ordinals.
The four most proment are:
Ordinals Wallet If not the oldest, certainly the largest
Magic Eden We know them from ethereum NFTs
Ordswap Personally I find this a vague one but they are well known through Twitter
Gamma it's quality that counts on this marketplace