I don't know if you'll ever come back to this, either to do a writeup or add to it, but it is quite wonderful! Sometimes I can just sort of sink into the image and see figures and detail. Here are the improvements that came to mind while I was playing with it.
It could use some more suit names. They're probably easy to come up with, but here are some I've seen on real decks: discs, mirrors, spirals, doors, chalices. And some from the short story "Dowager of Bees": chains, bees, ivy, scissors, chimneys, teeth.
I'd like it if some decks used "princess, prince" in place of "page, knight". Other face cards in actual decks include "brother, sister, mother, father". Again referencing Dowager of Bees, we have titles like "Dowager, Detective." It would be nicely surreal to have a wide variety of titles like that.
All that's just word-stuff, but with the images it feels sillier to suggest anything. One nice touch would be using textures other than gradients on some decks, as if the printing techniques vary. And the lines could be slightly offset from the colors, as is often seen on older or cheaper printings of RWS decks. Also, the style of the numbering and lettering could change from one deck to another; some decks could have a "borderless" style.
My personal temptation would be to add a few exceptions to many of the predictable rules, for example sometimes "six of swords" could be generated via the face card / major arcana generation algorithm.