Dead areas
Areas like Belle/Snowtown are totally dead.
Why not make treasure hunts in those specific areas.
Make a daily quest/mission for those areas. A reason to go there.
Team spar (red/blue room)
Some admins used to give hats if you could beat their guild (Anbu I believe was one of them) in GS. They would broadcast the event and 1k noobs rushed to the GS arena in swamp.
Why not do it with team spar? Certain number of matches would qualify for a reward. Doesn't have to be a hat, could be furniture, accessories, emotes, etc. I say team spar because it would be harder to win with randoms than with an established GS guild.
Loot
Add more items that turn into hats/items.