So here's the tip/idea to use:
Hang a grosgrain ribbon vertically and attach the cards to the ribbon. I chose a red grosgrain ribbon with white polka dots for this project then hot-glued the ribbon to a Christmas plaque I found. You could certainly hang the ribbon as is, like this photo from Life on Mars clearly demonstrates. Note: At first, I used mini clothespins to hang the cards, but it began to feel cluttered once all the photos were hung, so I switched to reusable adhesive putty (sticky tack).
Here is the full-length view:
After attaching all of our horizontal photos to our card holder I ran out of room for the others, so I moved the vertical ones to a door frame and displayed the folding cards using the slats of our louvre doors.
This was an inexpensive, easy project with a huge payoff for me. Our cards finally have an orderly display!