[knuthom]

The guy on the left looks more like this:

Painted Cheyenne
It is not identical, but seems to be similiar. Maybe he evolved to using photos as a basis for his own compositions.

Nah, too much work for a fraud like Churchill. He probably did copy it exactly from somewhere else.

[TaxRelief]

I am sure I saw the photo for that painting either in the Heard Museum in Pheonix or in the North Arizona Museum (?) in Flagstaff.