The WATCHERS OF THE WALL - POP IMPRESSIONISM T-shirt design is for the Game of Thrones fans that grew up in the 80's.
The concept is simply Jon Snow and his White direwolf Ghost standing on the Ice Wall. It has a Heavy Metal Magazine and a He-Man type blend for the style. Jon seems to have a bit more confidence and somewhat less brooding. Not the intensity burning from that characters' eyes.
As for the artwork, it is different than what you see elsewhere. First, the colors are far less dreary and much more bold. Second, The Pop Impressionism aspect brings a sort of Saturday Morning Cartoon feel to the piece. It is something that I can't really describe to anyone who wasn't alive in the 80's. Without losing that ominous vibe to the Night's Watch. Think Dungeons and Dragons if it was drawn by Simon Bisley or Frank Frazetta.