Okay, every time I watch the movie now, I see King Candy's graffiti, but I have yet to spot any Turbo graffiti. Still looking, though! And this picture is fantastic! Great job to both of you.
When Ralph is leaving Pacman to go to grand central station and then back to his game you can see Turbo's face on the wall behind him. It's hard to see because it's faded out,but it's there.