The Minecraft paintings are pixelated real paintings by Kristoffer Zetterstrand (except for the Wither one that got added later.)
So, I unpixelated these files back to a resolution of 512x (seeing this ingame feeled somewhat surreal!) Anyway, it's interesting to see these details, especially on the 1x1 paintings where you can barely see anything. I hope you like trying it out (or maybe even using it for a longer period of time).

You'll have to head on to Dropbox to download the pack, because it is a bit too large to be uploaded here

Also, I want to make clear that none of these art pieces is my work, it was all painted by Kristoffer Zetterstrand, I just put them into this Texture Pack