FBohler posted over on the forums an idea about having guild competitions, much like the individual ones we already have.
We have many individual competitions, like fishing and treasure hunt, but there’s no Guild competition so far.
My suggestion would be a guild based siege count.
Simple as that: every time a siege gets lifted, the guild of every player in the scene get one point. Make a leaderboard and give prize to top 3 guilds. As a really new mechanic, the prize should be a buff (of any kind, really) that lasts for a week, affecting all guild members.
Add your thoughts and suggestions on the forums here