Rain slowly builds, thunder and lightning continue to roll in. Road muddies, horse/wagon getting stuck in the mud. Thunder strikes coinciding with a deep hole a horse just walked in, horse panics, breaks its leg (maybe just sprain?). Horse is decompacitated and the rain just went from pouring to an all out monsoon. Shelter needs to be found, horse needs to be taken care of, covered in mud, add the posibility of items being lost to the confusion with the wind and dealing with spooked animals.

Marraige custom. The groom must prove his worth to the friends, family, and future wife. The best man is obligated to challenge the groom to a duel and the best man chooses the weapons. (can be anything, toothpicks, cotton balls, anything) If the groom wins then he proves his worth. If he loses then the bride will accept him for his faults and could sometimes gives him a task to accomplish before the wedding.

Facial tattoos in various designs are a sign of status in some cultures.

A low lying area will flood after rains causing many people to be stranded and many roads are covered with water and unuseable.

Religious city. Hundreds of vendors selling small statues which sole value is as a donation to one of the many gods that are worshipped.

The Chinese, when attacking a castle or fort, flew kites over the city wall and used the length of string it took to get it there as a measurement to know how far they had to dig a tunnel to get under the wall.

Termites, in certain places, make homes that can be eight meters high and only a half meter wide. They are built facing North to South to take advantages of the suns travel, maximum heat in the morning and evening and little in the afternoon. Imagine grassy plains with vertical structions facing a certain direction all over the place. Ambush? Maze? New creature? Larger structures?

Silk Armor? The Mongols wore silk undergarments under layers of leather armor. Why? Because silk is very strong. If an arrow hit them and made it through their armor, it would usually not have enough energy to puncture the silk. It could still enter their body but, because the silk would not break, the arrow's barbs could not do their work and the arrow could easily be removed leaving a relatively clean wound considering normal arrow wounds.

A new substance is found in an out of the way area and kept very quiet. It is found to make a perfect counterfeit diamond. Only the most expert of expert appraisers would even have a hope of noticing that it is fake. Only one problem: if it gets wet it starts to slime and if it is saturated, it turns into a glob of gel.

Another real world thing. White tea. Can only be picked two days a year, the two days before the flowers blossom. Could be a similiar plant that...is the deadliest poison known, cure known diseases or psychosis, or a potent herb that just tastes awesome.

A certain culture believes that evil can live beyond the grave. They also believe that the destruction of the dead body can keep that one from coming back. Destroying the newly deceased body can destroy the soul if done properly. They first burn the body for 24 hours, smash the remains as well as possible, then burn the what is left for another 24 hours.

Thieve's House or thier main front: All the floors are designed to squeak when stepped upon or to sag or bend sending a small shake along the beam, somewhat like a spiders web, to alert those inside.

Diseased people, (leprosy or any other such fear inducing disease) when traveling, will often times wear a cloak that entirely covers their body and ring a bell as they travel, used as a warning for any others to stay away. Could be used for a disguise or safe passage.

A large vertical cave has a constant, strong wind blowing out of it from the bowels of the earth. If one was to jump into the currents they would have a controlled ascent on the winds till they reached a height where their weight and the winds force reached equilibrium. Impossible to climb down naturally. What is it? Natural winds from the earth or a complex magical protection for an underground lair?

Mining in a certain area turns all exposed skin (maybe just parts that are actively disturbing the chemicals that cause the reaction) of the those doing the mining to a dark blue color. Will wear off taking as many years/days spent in the mine.

Custom among pirates to yearly vote for their leader. If a majority believed the leader was doing poorly they could hold another vote. Democratic except in times of battle and danger at sea. Could bleed that over to some 'honorable' bandits.

A comet flies through the sky every so many years. During this time no fire is able to be lit anywhere the comet is visible.

Sword sharpness is equal to the status and skill of its wielder.

A people who believe it is incredibly impolite to speak to anybody they meet for the first time. They believe their actions should speak for them until they are comfortable in each others presence and can then trust each other. Only then would converstation be appropriate.

During battle/war the heads of all slain are decapitated and collected by the slayer. The slayer will clean them up and put them on display for inspection by the commander. Depending on the deads name, rank, and expression on the face held by the death blow-the slayer will be rewarded by gold and/or status.