I made a card box, for holding Magic cards, a while ago, and I lined it with felt. While that does look good all the plastic sleeves I use get caught on the material so it is difficult to put them away.
Flocking seems like a good idea as well but I am imagining loose bits getting into the cards and it bothers me. Yes, I have never actually flocked anything before, but even if it all adheres to the paint I find it hard to believe that it will never fleck off.
What can I choose to line a card box with? It has to be something that will allow the sleeved cards to move freely and stay in its place. Being decorative is secondary, if it matters.