Because my focus has to be increasingly pointless so I don't bait myself into hoping the things I do with my time will mean anything to anyone, I have been going through the image files in Balatro and enhancing them pixel by pixel.
Noting that there are "1x" and "2x" folders of the same assets, I thought, well, does it use them both? Surely it can't be cross-referencing them every time it renders a card. So I used the full resolution of the 2x images to make clearer and easier to read cards, and was very pleased with the results in game. It's like having new glasses. So I've since been working my way through the jokers and tarot as well, adapting the original pixel art faithfully for the most part but taking creative liberties with the lettering for variety.
There are many jokers to go. I suppose I'll make the mod available somewhere when I'm done. It turns out that the game draws only from the 1x files for Soul, all of the celestials, and most of the spectrals. A mysterious process, but I am content to leave those be.