Popped over to the artist's imgur page and saw this:
"Due to popular demand, I will look into getting high-quality prints made
from the original images. I will announce when they are available.
Thank you for all your support, everyone!"

According to the artist, they are: "The wildlings are dressed like the Ainu, who are the indigenous people
of northern Japan. The Ainu are thought to be the descendants of the
first inhabitants of the islands, and throughout history they have lived
independently in the cold far north, beyond the grasp of the Emperor."