The current tabard is a simple blank item, linked to the guild; If you give my tabard to a member of another Guild, this takes the template of his guild and so on.
You could replace this system with a more realistic system:
The tailor (Skill Tailoring) creates a blank tabard and give it to an artist (Skill Artist), artist creates the guild herald. In this way the tabard will be forever with that emblem, though I give to a member of another guild.
You could also implement the ability to draw the emblem (idem for the paintings), or the ability to upload a .png file (makes it unique emblem for each guild).
The current system is so rough, We don't like to find other guilds with the same emblem or heraldry.