I like how you were able to capture the beautiful shadows in the flag. The wrinkling really helps to make it dramatic. Good composition. It help to bring the flag to your eyes.
This image relies entirely on its title. Without it there is no connection with that day other than the abundance of flags displayed around the world afterwards. As an image it could have been better composed by getting in closer to the flag and giving the viewer more to hold the attention. it's a nice crisply lit shot otherwise.
For me 9/11 is not Nostalgia, hense image does not meet the challenge. I do like the use of the tree to give a different background then sky for the flag. Question: If the flag is to represent 9/11 should it not be at half mast?