I am no longer surprised at the naïveté of most people, when it comes to things Native American. Not always are lines clearly drawn between anything. To suppose there is an "official" source, of anything, is, most definitely, a clear lack of understanding of Native American history, in-fighting, government impositions, rudeness, greed, and so forth. That the New Age movement has co-opted, and cobbled together this and that—usually resulting in a mish-mash with no comprehensible meaning to anyone—is an enormous tragedy, that has driven many traditional Native Americans underground, and done a further disservice to those Native Americans who, sometimes, already, have little of a rudder in this life.
The replication, reproduction, and manufacture of Native American arts and artefacts, leaves a great grey area of what is, and what is not representative of regional arts, and from whom (and where) the artist has ties. For example, in the Pacific Northwest, it is not unusual to see, in the city of Seattle, arts by Native Americans, that display the regional arts of the Northern Coast of British Columbia—which is clearly, not representational of the regional art of the Seattle area—why? Because the regional art of the Seattle area, is not as familiar, nor as exuberant with shape, line and colour as is that of the Northern Coast of British Columbia. Since such art is created as a commercial enterprise, based on the tastes and demands of the purchaser, the trend goes onward. From a politically-correct standpoint, that shouldn’t be the case, but many consumers are less than aware or educated about such minutiae as regional Native American arts of particular locales.
As for the Shawnee, and who is and who isn’t Shawnee, don’t hold your idea that there is a end-all or be-all authority of who is and who isn’t. I simple survey of the history of the Shawnee would easily dispel any notion of that idea. The Shawnee where forcibly removed from their lands, in four different sweeps—the government, in frustration, decided to vote, for the Native Americans, that those who they did get in those sweeps of relocation, were no longer Shawnee. Typically, the government kept issues stirred in the Native American communities, where traditional lines of culture, authority, and so forth, were replaced by government-picked authorities, approved culture, and so forth, further dividing communities (and creating a problem which exists even down to today.
For many Native Americans, belonging to the official, government-version of Native American, is a very bitter pill—some seeing such as "selling out" or becoming a "hanger-around-the-fort" or, more clearly, as an opportunist.
Although the shields may be representative of Native American models, and symbols—whether their derivation is from "authentic" extant sources, or are from the repertoire of regional art, is a moot point in some ways, and difficult to prove or disprove, in other ways. In a world gone crazy with consumerism, to what end would you have such an object? Of what practical use would it be to you? What is the reason you would be buying this? It is quaint to want to collect objects and artefacts from indigenous cultures, from the past, but what does this say about you? Is it status, usefulness, display, support for the artist, what?
Some indigenous people survive in ways that they see are harmonious to their traditional way of life. They live a very marginal existence—by modern standards. Some people choose to live without all the "mod cons" since those ‘get in the way" of traditional life. There are those who are so cut off from economic opportunities, that the creation of art, is one method of bring in a few extra bits of money to supplement things. Still, there are others, who are quite nearly mainstream artists, but who specialise in the Native American idiom—all Native Americans. From which of this rainbow of diverse existences, does one decide is the "authentic" representative? Such is not so easy, once one goes beyond the superficial debate of "where the store is located" and so forth, ad nauseum. The true question is what is in the heart—the artist’s and yours.