New Yorkers take a kind of perverse pride in never looking up. Not in a figurative sense, of course: we are, after all, as optimistic as anyone else. (Who else but die-hard optimists would willingly live in so unforgiving a city?) But when it comes to actually, physically looking up, most of our gazes rarely rise above the ankles of our fellow commuters. The Boston-born, New York-based artist Duke Riley is going to change that.