I've seen floor clings inside, but never one on the sidewalk.
Saw this one in Times Square
And this one on 6th somewhere around 17th.
(Man, that Sarah Silverman really gets around.)
The world is already saturated with ads; so if you're going to stick one somewhere, make the creative worth the intrusion. At least the Silverman one tries to play off the placement. Of course, Kirshenbaum Bond + Partners already did it better years ago for an intimate apparel company with sidewalk stencils that said, "From here it looks like you could use some new underwear.”