While doing research on heraldry so I could make better squad markings for my blood Angels successors, I came across the term "diapering," which would make for a rather interesting conversation... The term refers to an embellishment to a colored portion of a heraldric device that is a shade of the same color. Anyone who has seen any of the bretonnian knights that have won the golden daemon has seen this. Basically, it allows for a more artsy pattern in the heraldry, without changing the meaning. Here is the site where that had the info. http://www.rameset.com/heraldry.htm
Incorporating stuff like this into your painting is something that will take your army from good to great. Just don't overdo it.