Oh dear, where to start! First with 2 already mentioned: Marc Chagall and
Frida Kahlo. Not together
(although why not?) - but both brought something very new and significant to 20th Century art and both were slightly marginal as artists (Chagall as a shtetl Jew, Kahlo as a Latin American woman), yet managed to impose their art. I have no idea how their art would look on tarot cards. I suspect Frida Kahlo's would be more suited because she painted small paintings, very detailed, on smooth steel.
Next with a glorious classic:
Jan Vermeer. He didn't leave the "right" kind of paintings for a tarot - not even a set of majors - so we would have to ressucitate him and give him the commission. Given when he lived, I would have him paint 22 Majors, and 56 unscenic minors in any style he fancied. I think he would have brought a special illumination and "every day magic" to tarot.
This observant and tongue-in-cheek artist merits a deck...
Grandville...oh, but wait a minute...he is having one
...
Among the contemporaries,
Oswaldo Guyasimin might make some astonishing imagery for tarot -I'd love to see his "Hands of Fear" series translated into arcana - although he paints huge canvases, so it might be a challenge to get him to paint small.
In a much lighter vein, the cult comic artist Zep - a local boy made good! - and his
Titeuf might give us an irreverent deck
Chris Ofili, the British artist of Nigerian parentage, who made everyone gasp with the elephant dung he added to his witty canvases would no doubt make a very zany deck
For you Londoners out there - he's showing at the moment in the Upper Room of the Tate.
Finally,
a Pre-Raphaelite deck would be beautiful - I am surprised none exist! - as would a deck made up of
Medieval illuminations of books. Without trespassing on the ground covered by the Golden Tarot, I think some careful exploration would bring us some marvellous medieval imagery - energetic, funny, dark, deep and very eloquent, as was so much of medieval imagery.