I love this idea! Yes I also think that this should be free. Also, I think that you could have a certain deal depending on the guild hall you buy. Here is the deal for each guild hall:
DEFAULT: Shield only for guild master
SMALL: Shields for master and officers
MEDIUM: Shields for Recruiters, officers, and master.
LARGE: Shields for all!
Also, to design it, there should be a tav for the guild master to create the shield design. Then he/she could post a thread showing the finished product, and the guild members decide if they like it ir not! I encourage this idea to be shown to the game developers. Bye all!

-Mastercon