You know those temporary tattoos you used to get in Cracker Jack boxes?
Well, you can do something similar at scale with concrete. You print the painting onto plastic sheets with UV-resistant mineral paints (using industrial ink jet printers), then while the concrete is still wet, you apply the plastic paint-side down onto the wet concrete. Once it cures, you remove the plastic, and voila! you have a fresco of the image embedded into concrete. If the concrete surface is old, you can apply a skim coat of concrete epoxy over the top of the old concrete (to create a new, wet surface) and do the same.
I'd like to see the technique used to make Christian's art more widely accessible, on fences, industrial buildings, sidewalks, etc. If you tied a non-exclusive right to reproduction in this way, I could see his NFT's becoming quite valuable.
Mineral paints can last at least a 100 years in full sun/weather, with little touch up required.
There's a company already doing this, I think, but i can't find their web page now.
https://www.keim-usa.com/Mineral-Story/All-Mineral-Pigments
https://www.keimpaintshop.co.uk/products/concrete-paints
https://www.creativebloq.com/print-design/giclee-printing-11121324
https://blog.lexjet.com/2013/03/25/inkjet-printed-wall-murals-illustrate-military-history/
https://www.youtube.com/watch?v=zw00amZ3R0U
https://www.youtube.com/watch?v=eLrrt8MRq8M
https://www.snazzylittlethings.com/diy-large-scale-image-transfer/Lar