Well, if the picture is meant to be based on the books, then the location must be somewhere in the far east of Middle-earth, because there is no Saruman in there, meaning it shows the Blue Wizards after Saruman departed and returned to the west. Who knows, some old forgotten mountain chain in the east, maybe where the fell beasts came from?!
I must agree, I also like it because of the mystery surrounding their mission and its outcome, we really don't know anything.