There is a small and strange nature-worship cult that has dedicated itself to freeing vegetables. They appear usually in working pairs or trios, arriving to villages and towns separately and wearing the local garb. For some reason, they have taken to disguising themselves specifically as a scholar, a cooper, and a fisher. At night, they will sneak into backyards and side gardens, digging up household fruits and vegetables. They pile the pilfered plants into a cart and vanish in the night. While the townsfolk wake up to empty gardens, the cultists replant the fruits in the wild to let them be "free".
Gnomes are famous for their festive springtime celebrations. Farm villages will often dye their hens eggs bright colors; with gnomish magic, the chicks that hatch from the eggs have the very same colors. The chickens eventually lose their hues, but the stronger the magic, the longer the color stays. In a gnomish village, one can easily spot the village shaman by his flock of gaily colored fowl.
Rich Romans raised fish in private pools at their villas. A favorite fish was lamprey, a parasitic fish which sucks off blood and flesh but made an excellent meal. A particuarly gruesome punishment for slaves was to be thrown into the lamprey pool, where their flesh was ripped from the bone by swarms of the jawless fish.
In ancient Rome, social appearance and respectability were everything. The most hated men were punished with damnatio memoriae, damnation of memory. Every trace that a person had ever lived was removed. Busts were shattered, freizes were marred, records were struck. Any sign of the hated figure was destroyed.
Medieval Britons didn't write contracts. Instead, men making agreements would clap their knives onto an altar and recite the agreement three times to seal a deal. Even after the Normans introduced written contracts, British nobles would wrap the parchment around a knife to authenticate it.
The PCs are sent with a diplomat to another country to protect him and do his bidding. There may be some espionage, rescuing, downright bullying, etc. Could make a nice medieval, special operations background.