Hmmm. I think of the cards almost as orders or order opportunities in the game. Orders were written in an order book, probably at some point the result of referring to a map, from a map case - and a book and case would be: leather bound!
So - I tried a texture showing a leather binding style, and I like it! I also changed the card back to make the title more visible, and more intense (red) representing the drama and tension of conflict.
So, here are a couple of samples:
Argh. I still can't get multiple images to load. I'll post the card front example in a new post.