The furniture currently available is rather lacking - there's only a small number of room varieties you can outfit, and it doesn't help the existing chairs and tables look like garden furniture. Namely, it's lacking in decoration for lounge areas. We could certainly use couches in the Spiral line, as well as coffee tables and other decorative items to make the place feel a little more homey.
In terms of functional items, I think we'll all agree a floating hologram text (like the one you see in a terminal and with artifacts) is going to be of great use to all guild hall curators - the MotD is not enough to convey all of the information that's important for a guild. Greeting messages, Hall-Of-Fame and memorial types of rooms, detailed information about guild events (you can only fit a small announcement in the MotD) are some of the uses that come to mind.

So to recap it all with a list:
Holo-text
Couch
Sofa sections (regular, corner, island)
Coffee table
Drinking water fountain
Decorative water fountain
A lamp that's sitting on a Table or Chest of drawers
Taller plants (like a small palm tree or decorative rubber plant)
Fish bowl

And other items you may suggest.