Mike Butcher did something similar for his Saxon army. I liked the idea so much that I completely stole it and did my own. WAB uses shieldwall rules for the rank and file and so these are eye candy markers for gaming purposes.
It was also a good way to practice painting shields, again I was looking to match my rank & file thath will have some with the Little Big Men transfers. Based much like my army.
I think this was a cool idea. The shields were some metal ones leftover that Mike sent to me.