I am so disconnected from the tarot, and almost even uninterested, that it wouldn't feel fair to design a deck. I feel it would ruin it.
Tarot aside you could make a non-traditional card set. While most card collectors think about sports cards there are a lot of collectors that focus upon what is termed Non-Traditional card decks. Non traditional decks include artists regardless of genre, things like Mars Attacks cards, the old Wacky Pack card series, ships and transportation, heck even the most wanted cards that were issued for Iraq. Lots of potentials there. Number of cards per issue often varies from genre to genre though many of them have something in the order of 50 cards per deck though Disney type cards tended to have something like 25 per deck with a few special foils, 3d or puzzle type cards included as well.