[Without having seen Prompto's barcode, it's hard to give him specific examples of what could take its place. Fortunately, Ignis does have a bit more creativity than those who know of his penchant for logic would give him credit for.]

A simple solution would be to black it all in and then create a continuous band around your wrist, much like the bracelet you now wear. It wouldn't be all that unusual. I've seen many a person with such bands around their arms. Of course, unless you were dead set on something like that, I wouldn't settle for such a basic design.

[Only the best for his Chocoboy.]

I'm sure a talented artist could make the lines into any number of shapes and then work them into some kind of picture or pattern. Flowers, trees, vines growing up from the ground, for example. Perhaps part of a building or a road, and those are just solid objects. I'm not even touching on the limitless geometric patterns one could work it into even if is just a base to begin the pattern from.