Here we are at the very end of the A-Z of World Building, with Z for Zoology.
Animals have always played a vital role in the world of humans, whether as food, clothing, labour or company. While you may not be inventing any fantasy creatures for your world, it is still important to look at which your people value and why.
An animal that is viewed as a pet in one culture may be food in another. Are your people wasteful, hunting for small parts of animals or for sport? Or do they use every part that they can and let nothing go to waste? Do they see themselves as dominant over animals, or do they revere them and thank them for the part they play?
Think about which animals are domesticated. Humans don't bother domesticating, feeding and caring for animals that aren't of any use to them, even if that use is mere companionship. Which animals do they use for labour? Which for meat or other resources? They are unlikely to breed an animal that gives them very little meat, but they may if there is no alternative, or if it is considered a rare delicacy.
Which animals fear humans, and which do humans fear? Humans may not only fear animals that want to eat them, but religious beliefs may also make a particular animal fearful or sacred.
The relationship between your humans and animals is a very important one. They all exist together in your world's foodchain, whether your humans sit comfortably at the top of it, or a little further down. And what happens if a new animal suddenly shows up in your world? What happens if it's an ultimate predator?