Ordinary merchants are ok but fantasy or surreal ones are more intriguing.
I tried to design some with Carys. We each drew four merchants (and later Carys drew a extra one), then with help of Brian we wrote 6 items for each merchant.
You can find the resulting PDF here.
Bonus content: a itinerant merchant generator
The merchant... (d10)
- is a headless artificial construct or a golem
- is a monster wearing pretty clothes
- have been cursed with a animal head and can't speak humanoids languages.
- wear a veil and speak softly
- wear a old suit of armor and a sealed helm
- is a insect using mimicry to vaguely look human
- is wearing baroque clothes from a other plane
- wear a beautiful and elaborate magical prosthesis
- is a unknown humanoid specie wearing common clothes
- is chained to a strange familiar
and is selling... (d10)
- Dentures and wood noses
- Keys and doorknobs
- Traps and whistles
- Gloves and ribbons
- Belts and girdles
- Tiny chests and boxes
- Optical devices
- Achronistic items
- Clockwork pets
- Miniature idols
Each time the group encounter the merchant they have a unique special item to trade or sell. If you need to improvise a item, ask one player to describe something that attract their attention, then ask a other player what kind of special property the item could have. If you need more details ask a third player, etc. Take notes and tweak their answer a bit using "yes but" or "yes and".
If you are using the merchants from the PDF roll on their items table to determine the item. This way the players can wonder what the merchant will have the next time they will encounter them.