Novel take on the challenge with a long exposure. I guess an effect with all people moving but one lone figure would have a lot of effect but hard to arrange :)
I like the time lapse, some people still, some moving. I would try and go back when the sun is at a different angle to the window as it was at this time.
Nice image but I don't see the challenge being interpreted here. I can understand the fact this place is huge and you may be looking for someone but...
I don't get how this fits into peek-a-boo, but that being said, I do like what you are communicating. As a shot, well done. In this challenge, I have to say "Huh?"
I love how everyone looks perplexed just standing there, except of course for the one's that know exactly what they're doing, as evidenced by their blur. Very cool capture and idea.
Lovely shot of Grand Central. I like the contrast between the color tone and the people standing which portrays calmness vs the blurred walkers and the location which hints towards urgency.