Native Americans led the way in engineering the canoe as we know it today. They used natural materials to the fullest extent possible, even taking advantage of a property of birch bark in creating their decorative designs.
Birch bark, when removed from trees in winter, has an inner bark rind. This inner rind was scraped away to create the designs, much like a engraver etches a design into a material. When the bark was formed into a canoe, the bark from the outside of the tree faces the inside of the canoe, while the inner bark becomes the outside of the canoe.
Ojibway canoe on the edge of a lake - date unknown. From Smithsonian Institution Glass Negatives of Indians (Collected by the Bureau of American Ethnology) 1850s-1930s
Not every canoe had a design. As a matter of fact there are a limited number of references on Native American canoe designs. Of those documented designs some are thought to be tribal related while others could have been a reflection of individual creativity.
There may have been outside influences in some Native American designs. One reference states that a specific design was based on a Pennsylvania Dutch Hex design. I would guess that, much like artists today who are influenced by someone else's work, they may have incorporated what they saw into their own style.
If you come across a design that you can document as to authenticity and time period let us know. We're always on the lookout for more designs.