"The Cetemi have a most curious custom that in their celebrations must all men don the garb of women and women... the garb of men, to the aim that none shall... know another." -An Account of Barbarian Lands, Lord Shakthur
"It is said that among those people they have a loathsome custom- that they keep a spotted dog always waiting beside the gate of the yard where they bury the dead, and that in every funeral they allow this spotted dog to feast upon the dead, so that it grows fat and wise with the knowledge of the dead... Many necromancers do seek out these spotted dogs, and ask of them sciomantic knowledge, or take them as familiars." -Author unknown, "The Ways of the Necromancers"
A certain culture has a curious pass-time- muscle art.
Muscle artists (who are called by a special name) work hard to sculpt their bodies, trying to become as muscular and buff as possible. The best among muscle artists look almost grotesque in their amazing muscularity, Atlas-like giants with shiny, oiled iron arms and legs.
In a certain nation, no-one except the Emperor is allowed to have a name. Therefore, the people give themselves pseudo-names called "callings". Examples of callings: A family is known as the Red Sparrow family. The father is called Swooping Red Sparrow. The wife is Bright Red Sparrow Blue Lizard because she was called Bright Blue Lizard before marriage. Their daughter, until she becomes an adult, is Daughter of Red Sparrow. Their sons are Eldest Son of Red Sparrow and Younger Son of Red Sparrow.
"...The people of the Dalaben Fens have a custom heretical to our superior Zodashan faith, in which they place their dead upon the grass roofs of their stilt-houses. It is said that they do this because they used to bury their dead before the great Judgement, in which their home became the swamp which it is today."-Sir Edrosh Metorva, "The Barbarian Lands of the East, Volume X."
A culture believes that souls are recycled. One child gets half of a soul, another child gets the other half. However, this means that with each passing generation, the amount of soul in the child will become less and less (Through division)until their culture will die in the future because of their soulless offspring.
The PCs come across a wild thicket of luscious looking blackberries. They eat the berries and become drunken fools. Later they find out that the berries were part of a fae garden and were intended for fae wine. In payment for stealing the berries, the mischievious fae make life inconvenient for the PCs. Horses are untied, water skins are drained, spare clothing is drug into the water, etc.