TH,
I was hoping that Gray Wolf would chime in here with a few pictures from his archives. There's no single best source on this. Its pretty much catch as catch can. Cast brass tacks are the #1 decoration for NDN guns. These tacks are once again available but are pricey. The Trunk Shoppe in Colorado makes them and they can be found via google. A lot of western NW guns were tacked. There's some examples of tack patterns in the Trade Gun Sketchbook put out by the Museum of the Fur Trade. You can find a bunch of tacked guns scattered around through different sources and there are even two rifles reputed to be owned by Kit Carson that were tacked. Here's an NDN example attributed to Chief Joseph of the Nez Perce:
http://www.nps.gov/history/museum/exhibits/nepe/exb/contact_change/1877War/NEPE9741(2)_Rifle-Detail.html
Rawhide is also common on these guns but was used more as a reenforcement for breaks or lost pins than a decoration. There's a drawing of a gun in the Mountain Man sketchbook volume I that is rawhided almost stem to stern. It started out life as an 1840-50 Leman NW gun, but the wrist was broken and the barrel was replaced with a rifle barrel. There are no pins or bolts holding the gun together just a stitched tube of rawhide from the wrist to the RR entry. Rawhide patches were nearly always stitched on wet, not tacked.
There's a start. Lets see if someone else adds more info.
Sean
