Love it -- I would simply take a brown marker and draw freehand some straight lines along the blue -- to make like a border. It really finishes off a card or page. and the lines don't have to be straight and can cross over each other --
here's an example (sorry it's not a great pic) but see the stamped images and how they are in that "square" ...well, it's just drawn in -- 2 semi-straight lines. It kinda finishes off a picture or image and would look great along the blue part of your swap.
4 card gift set with purse by wiggydl at Splitcoaststampers