Optional! TT HQ ideas: Eventually it'd be cool to have an area for bending training. Something like the pro-bending training room from LoK. Air and firebenders don't really need anything (except, y'know, fireproofing), but a net with clay disks for earthbending and an open source of water (a tank or reservoir of some kind) for waterbending. The training room that's pictured has weight lifting stations, punching bags, and what looks like a few balance beams and even a springboard, for strength and agility training. That way it wouldn't just necessarily be for benders; anyone could use it. :D
Addendum! Spinny boards of doom! More agility training! >D