To actually put an image (not just a link to the image) on the Bitcoin blockchain would be very expensive. And any other chain, well, maybe it won't be around that long. You can put a hash of the image onto the BTC blockchain, there are plenty of BTC notary services for this exact purpose (either tools/wallets or websites which can do this). A hash would prove the image existed at a certain point in time, and you can use it to prove the image you have hasn't been modified. Not an NFT. I don't have any specific apps for this purpose to suggest.
Discussion
I know it would be expensive, but I don't know in which range tbh. Maybe I decide differently when I see the cost 😅 hash is a nice idea but not really an option for me. It's either the picture itself or nothing
Look at sats/byte here and you can figure your image cost from there. Note that your image would actually cost more since you can't use all the bytes for image storage, some would be for image data, and you may have to split the image into multiple transactions.
At 4 sats/byte, 1KB is 4096 sats, 1MB is 4194304 sats which is $4,000 USD if I'm doing that back of the napkin math right
Oh wow, thank you for checking this and the info. I would be willing to spend a bit, but 4k is a lot. I gotta check how much I can scale this down 😄