The Nebraska State Historical Society recently announced that it has put is collection of over 2,400 Native American artifacts online. It’s almost complete and available at http://pastperfect.nebraskahistory.org/unicgi/mwebuni.exe?request=ks.
I did a search for Lakota and got 276 records; when I refined that to just records with images I got 245. Results are presented with thumbnail image and item name. If you click on the image you’ll get a larger version, but I encourage you to click on the purple arrow icon instead; that’ll give you a lot more information. Information on an item detail page includes object name, thorough description, dimensions, material, and history.
Some items had additional images to show detail, like this closeup from a beaded dress.
There’s a lot to see here — do a search for Native American if you just want to browse for what’s available — but I found some collection highlights by doing individual searches for quillwork and beadwork.