I heard guild housing is coming in a later patch, not sure if Zeni is working on this yet but if they are I could give some suggestions.
1. a walled off section in a city that is accessible by a door.
2. when you use the door it sends you to an instanced location that is only accessible to your guild.
3. you can see and interact with other people of your guild
4. it is a large courtyard and with a building like you see in cities
5. outside is a blacksmithing, tailoring, and woodworking stations
6. inside the house is alchemy, enchanting stations with a kitchen for making food.
7. in the courtyard and on the house there could be guild banners that have your custom picture.
8. interactive items like chairs to sit in or maybe minigames to play with your guildmates, gambling?