From the time that humans became self aware and started decorating we began trying to represent the world around us. One of the many categories of things in our vast world is animals.
We began over 40,000 years (1) ago with incredibly simple scrawlings on cave walls and developed from there. As time went on the scrawlings became more accurate and moved to pottery as well as sculptures or stone carvings, and then to metal. The works then became more intricate and fanciful. The different cultures developing around the world intertwined the animals in different patterns and gave them meanings.
The African cultures (Egyptian), Arabic cultures (Assyrian, Babylonian,Sumerian), and European cultures (Celts, Germanic, Icelandic and Norse tribes) all used zoomorphic art to represent their gods and ideas. There are many other cultures that have done this as well but the list will get out of hand so I'll stop there.
This is a part of what zoomorphism is, creation of patterns by manipulating animal forms. It is the morphing of traits of one animal or animals onto another as well. In most cases it was also anthropomorphic as we applied human attributes or ideas to the animals. This is similar to the eagle representing strength, supremacy, and power to the Romans. The eagle did not actually "represent" these ideas, but since they felt that way about them those were the traits that were associated with the majestic predator.
So, in closing, throughout history our peoples have made images of animals to decorate their abodes, their bodies, and their temples. I personally believe that these practices will continue until the end of time.
You can see some examples of zoomorphism by clicking here.
(1) National Geographic, Lubang Jeriji Saleh cave in Borneo, Indonesia.