Quick aside: Always irks me when someone says “Blockchain” singular, like it’s a proper noun entity cargo cult god. “A blockchain” is a particular type of data structure akin to a decentralized linked list, or in the context of one particular cryptocurrency you’d say “the blockchain”. I know that the crypto VCs use the word in that singular proper noun way, but they’re doing that intentionally to cultivate a misplaced reverence and we shouldn’t ape them.

Anyway bitcoin core v30, which just released, expands the maximum data size of a non-monetary transaction parameter called the “OP_RETURN” from 80B to 100kB, meaning that normal bitcoin transactions really can now store plain old jpgs with basically zero extra encoding. It was a wildly controversial change within the dev community, some people probably being paid under the table to push it through etc, but yeah it can do that now. I assume that some blackhat has already put CSAM onto the blockchain in protest.

However at this time you only have to pay < 0.2 sats/Byte to almost guarantee your transaction goes into the next block, so absent miners showing discretion and refusing to mint big OP_RETURNs, that 100kB transaction would actually only cost about 20,000 satoshi, or ~22 USD.