Flags of the high seas.
Sickle Moon Flag: This is the first of the flags available to Link in the decorations trading sequence of Wind Waker. I totally, Link must trade either an exotic flower or pinwheel to one of the traveling merchants to obtain this flag. Link can trade this flag for the next flag in the series or a fountain idol. These flags are also decorations that can adorn joyous pedestals on Windfall Island.
Sailing among the countless islands of the Archipelago means visiting a thousand countries and countless more holds, parishes, counties, and clans. Pride ensures each of these petty fiefs has their own unique flag. This means sailors must have an encyclopedic knowledge of flags, standards, and banners if they don’t want to accidentally steer too close to a rival ship.
----------
Banner items can be a fun way to incentivize your players to gather tightly in an otherwise inadvisable way. You could also have each of these flags be a trophy, or just invite someone to make their own flag on one of the blanks.
Be excellent to everyone.
-Ceph