There are several major tarot publishers (it's in a post on the Deck Creation section, you may have to go through the archives a bit). They do usually list what they're looking for, how to submit your art to them, etc. The two in the USA are Llewellyn & US Games. Italy has Lo Scarabeo (they use their own artists), and there's a Swiss company A.G. Muller. Usually they buy rights for cards (not t-shirt rights or mug art, etc.) and they get to keep your artwork originals (they need them for doing second printings, etc.).
There are several smaller companies that do this too, but they're much harder to find. And then, there are artists who publish their own decks because they either want to, can't get a publisher to pick them up, or because they only want a limited run of the deck & nothing else. Or any of a number of other reasons too, I guess.
But the major publishers handle all the details, want the art size a certain size, want input on the back image used, and basically stick their fingers in everywhere because they want to make money at it & feel they know best. They're also backlogged with decks coming out, so have it all lined up for the next 2 or 3 years down the line already. You'd have to 'get in line'.
Take a look at the main sites for the major companies. See what they list there. Also take a look at the types of decks they've already published--if they focus totally on historical decks, for instance, they're not likely to go with a theme deck that's modern. But you never know!
I believe there's info, too, in the several volumes of The Encyclopedia of Tarot. And members here can give more advice on it all, as well.
