The show and its characters are fantasy, but the novels on which they are based, written by George R. R. Martin, were inspired in many ways by life in medieval Europe. The original use of heraldry was to act as a sign on the battlefield, so that knights fully clad in armour could be easily distinguished one from another. The common practice was for a knight or lord to display the same design on his banner, cloak and shield.
You get: 1 awesome coat of arms to share with the world or put up in your house (or castle!). File will be a 800x800 px PNG file, that's great for web or letterheads.