I would love to to design a guild tabard but come on…
Window is so small its hard to see which color you choose for border and icon. I have 3440 x 1400 resolution and the part of the window with the tabard itself is no more than 1½x2 cm.
And forget it if guildmaster has a big beard… then you cant see anything. Make it as big as when you visit the barber
Agreed, in the age of transmogrification we should be able to customise it more. Perhaps even add elements from real WoW factions if the guild master has access to their tabard.
E.g. take a faction tabard, say Order of the Cloud Serpent, or even just Thunder Bluff, and customise the colours. That would be great for some guilds who want to show close allegiance with a certain faction but retain some personal identity.