As a designer myself, minimalism is the toughest style to master in playing card design. You can't go minimal for the sake of being minimal. It has to be functional, attractive, and balanced - and it needs a theme. Daniel Madison has had some great success with minimalist decks - but then again, some of his decks are too minimal in my view. Most notably, his blank deck lol. The Rounders deck is a good example of being very minimalist - yet meeting the proper criteria of what makes a successful deck.
The Fulton's decks are another example. Chinatown and Ace Fulton's Casino decks aren't as minimalist as Madison's decks, yet they are very minimalist when compared to much of what's out there with so much detailed and intricate artwork. The Fulton's decks have probably been my main inspiration - second only to the early 20th and late 19th century classics from USPC, Dougherty, and the like. I'm still in awe with what artists in 1896 were able to accomplish.
I would start with a theme. And experiment with the bare minimum required to present that theme attractively. I wouldn't go too minimal on the pips and indices to keep the cards fully functional - but try maybe working on the back design first. Just my 2 cents. Good luck!