Here's an idea that just popped into my head---although I don't know this deck at all... Have you thought about changing the hieght-to-width ratio? You could extend either the tops or the sides by gluing another piece of card stock (nice of course! for example, hand pressed/homemade paper like 300 lbs. weight watercolor cold press) to the backs so it's more of a square and less a rectangle. It may make the deck more ergonomical for you. You'd have a nice, additional white (or some other color paper) border that would be softer than the standard cardstock.
But looking at the cards via google images, they seems already quite square. If you own the deck, surely there wouldn't be aproblem with making a record of the original (hrmmm dare I mention scanning? for personal home use, of course) and then trimming them? It looks like it would be a great candidate for trimming. In fact, for my personal taste, the borders seem like an afterthought perhaps from the publisher. The artwork as it stands alone is fantastic---and I am no fan of angel decks, lemme tell ya...
ETA: It seems like you could still trim off a whole lot and only lose the titles (which are a bit "polyester-suit-ish" sorry Doreen!) at the most. Would be a great candidate for a trim job, fo shizzles.