Weren't tribes and shamans also directly associated with European Picts in Howard's Conan stories?
The most notable shaman in Howard’s Conan stories is the Pict, Zogar Sag, in Beyond the Black River. Picts also feature prominently in The Black Stranger. They are described as white, but are not regarded as such by their Hyborian neighbours. They have the trappings of Native Americans – warriors are called braves, wear feathers on their heads, "naked except for scanty loin-clouts", use dugout canoes, store their bows in "buckskin cases", wield axes, and take scalps.
Beyond the Black River (1935)
"The Picts were a white race, though swarthy, but the border men never spoke of them as such."
"No white man has ever plunged deep into that fastness [Pictish wilderness] and returned alive to tell us what he found."
"Balthus saw a lean figure [Zogar Sag] of middle height, almost hidden in ostrich plumes set on a harness of leather and copper. From amidst the plumes peered a hideous and malevolent face."
"He felt the eyes of the Picts upon him – hundreds of hungry, cruel eyes that reflected the lust of souls utterly without humanity as he knew it. They no longer seemed men; they were devils of this black jungle, as inhuman as the creatures to which the fiend in the nodding plumes screamed through the darkness."
The Hyborian Age (1938)
"[T]he Pict remained the eternal barbarian, ferocious, elemental, interested only in the naked primal principles of life, unchanging, unerring in his instincts which were all for war and plunder, and in which arts and the cultured progress of humanity had no place."
The Black Stranger (1953)
"They were dark-skinned men of short stature, with thickly-muscled chests and arms. They wore beaded buckskin loin-cloths, and an eagle’s feather was thrust into each black mane. They were painted in hideous designs, and heavily armed."
"The first to reach the crag was a brawny brave whose eagle feather was stained scarlet as a token of chieftainship."
"Blood-smeared braves dived howling into huts and the shrieks that rose from the interiors where women and children died beneath the red axes rose above the din of the battle."
"A feathered chief wheeled from the door, lifting a war-ax, and behind the racing Cimmerian lines of fleet-footed braves were converging upon him."
"I might as well leave you for the Picts to scalp"
Another shaman makes a brief appearance in Queen of the Black Coast (1934) as one of Bêlit’s crew, who all seem to be black people. "Bêlit... is a Shemite woman, who leads black raiders."
EDIT:
There are a few other shamans in Howard's Conan. Two are mentioned in passing in The Hour of the Dragon (1950). "[A] feathered shaman of the barbarians", probably a Pict, and a "Pictish
shaman". The fragment Wolves Beyond the Border (1967) has two shamans. One is "the Wizard of the Swamp... a pre-Pictish shaman". The other is a Pict, "old Teyanoga of the South Hawks". "A feathered shaman was dancing between the fire and the altar, a slow, shuffling dance indescribably grotesque, which caused his plumes to swing and sway about him: his features were hidden by a grinning scarlet mask that looked like a forest-devil’s face."