My knowledge of PNG is cursory, but my general impression (from a case study I read on the Dani specifically in college) was that their culture was nowhere near as sophisticated as that of the PNW cultures.
My impression as well. Without the stimulus of long-distance coastal trade/raiding and the 'technology' required, they seem to have had a much lower political and technological level, and of course any cultural development was side-tracked by the Cargo Cult phenomena from WWII, which has warped whatever casual knowledge the general population might have about them. They'd be a hard sell as a Civ inclusion.
I think a case could be made for a unique Monument or a Unique Improvement. Or the Crest Pole could simply be a unique Monument graphic (like Korea's) and the ḵwaan could be the Unique Improvement like I suggested above. I think a PNW civ would have a lot of options for how the dev's design it.
There were 6 different kinds of "Totem" or Crest Poles, but not all require modeling for the game:
Frontal Pole - in front of a family dwelling to show who lived there - an elaborate house sign.
Interior Pole - a highly decorated/carved roof support
Mortuary Pole - a pole depicting an individual who just died, with a 'grave box' included for the skeletal remains
Memorial Pole - a more permanent monument to somebody important, usually put up a year of so after they died, and the Mortuary Pole was no longer enough for a remembrance.
Welcome Pole - or 'boundary pole', put up to mark the limits of a tribe/clan's territory. Frequently on bluffs overlooking good fishing ground, at stream crossings, etc. It was also more specific in that all th examples come from the Nuu-chah-nulth ('Nootka') and Kuukwake-wakw ('Kuituitl') tribes only.
Shame/Ridicule Pole - (my favorite!) put up to embarrass somebody, either local or foreign. The Stephen Colbert or Herblock of poles.
The Interior, Frontal, and Mortuary Poles are either individual or temporary, so I don't think need to be considered as a Civ component. The Memorial Pole comes closest to the 'Monument' in form, placement and Meaning, the Welcome Pole would really be an Improvement, and the Shame Pole would be a Unique 'Special'.
A possible mechanism to include all of them might be:
Crest Pole. A Monument replacement fo the Tlingit/Haida/Chinook/Salish/Snohomish/Pulyallup/Steilacoom/Nootka/Kuituikl Civ. Gives +2 Culture. You may pick one other Bonus:
Welcome Pole - when complete, Pole allows you to add one contiguous tile to the city radius at no cost in Culture or Gold.
Shame Pole - when complete, may pick one type of Governor and any Governor of that type from another Civ has no effect on this city.
Memorial Pole - provides +1 Loyalty to this city.
At any time you may 'tear down' (eliminate) the Crest Pole and build a new one in the City with a different Bonus.
My preference for a Unique Unit is leans towards the Head Canoe: a distinctive Galley-Replacement with coastal raiding capability which also, when placed on a sea Trade Route, would extend the range of that trade route, or when placed over a Coastal Resource, would increase the yield from that Resource, neatly covering its multi-use function.
Also, and appropriate based on RL History, upon getting Cartography, the Head Canoe could be cheaply Upgraded to a Caravel-equivalent: Head Canoe with sails - graphic change only from regular Caravel (the PNW natives did this so fast after seeing the first European sailing vessels that many later commentators thought they had independently invented the sailing rig!)
On the other hand, the wooden-armored warrior is also an absolutely distinctive graphic for a Unit (Warrior replacement?) with, say, a Bonus against Ranged fire (from Ranged units, not Siege!)
We could have the
Kwaan as a Unique Neighborhood-replacing District, perhaps available with a Medieval or Renaissance Era Civic (although none leap out as appropriate at the moment), providing extra Housing based on number of Woods or Rainforest tiles adjacent plus Loyalty and Culture as 'bonuses'.