The other references mentioned so far have been to northwest coast art. This is rooted in traditional pre-contact work, makes great graphics and there are a number of books available which will show historic and modern designs. The seminal book on the design principles of this art is by Bill Holm, and Jim Gilbert and Karin Clark have written two excellent books (Learning by Designing Pacific Northwest Coast Native Art and Learning by Doing ...) which break down the elements and help you into the creation of your own designs.

I think this is what most people think of when they think of "Indian Art" and I plan to use an image based on it on my next kayak project. However these were canoe people and not kayakers, so there is perhaps some cultural discontinuity to use them on a kayak. If you want to use actual inuit designs on your kayak (which the inuit themselves did not, as far as I know) then you can look to the well documented inuit graphics from such places as Cape Dorset, Baker Lake and Holman Island. There are many marvelous images here also, but the inuit graphic tradition is modern (mid 20th century) so the work should in most cases still be regarded as proprietary.

After that rather pedantic rant, what do I actually think about it? Putting a Northwest Coast design on a kayak is not exactly culturally kosher, but so what? Unless you're going for an actual reproduction (and there aren't many sealskin boats being built these days) the kayaks we build are cultural hybrids anyway, so use what pleases you without ripping off someone else. Or get creative on your own. Ted Henry has built a Pygmy Arctic Tern with a great inlaid design based on the boat's namesake.