Client Paintings is a simple, *fully client-side* mod to add new paintings via resource packs while keeping the vanilla paintings intact. It achieves this by looking at the UUID of the painting entity and applying a pseudo-random algorithm to it to determine which painting to render.
This mod uses a custom resource pack format to add new paintings,
you can use the Client Paintings Pack Generator on my website
to generate such a pack easily. Alternatively, see the resource pack format section below for technical instructions.
Discord: https://discord.gg/WcYsDDQtyR
With the included default resource pack:

What vanilla players see:

I wrote a very nice and clean explanation of the resource pack format, but curseforge has some kind of aversion to my markdown, so I'll just link to the github README here:
https://github.com/enjarai/client-paintings#resource-pack-format
No files available for download.