I'm about to start DMing a North American-inspired campaign (later period than NC, although using some elements from both that and regular D&D) with my friends, and I've been keeping track of websites that have good images of under-researched topics like native arms and armor beyond stone arrowheads. It occurred to me that it might be useful to some of you all to have something to base descriptions on, so here's a few links:
For the Five Nations, check out George O'Connor's "Journey Into Mohawk Country". It takes place a couple decades before NC is set, and in the real world, but his sketch notes and the comic itself are a good visual resource, especially for the armor and weapons of the Iroquois Confederacy. Check out some sketches at http://www.firstsecondbooks.net/authors/oconnorBlogMain.html and sample pages at http://www.firstsecondbooks.net/BMR/journeyBMR.html
A good general resource for native characters is http://www.nativetech.org/, which even has guides to actually recreating most of these items with materials you can probably find within an hour's drive in most states.
I'll add more when I have a bit more time, and if there's more interest in what I've found.