What types of things impress colleges?

I received a letter form my first choice college today and sadly I have been placed on their waitelist. Enclosed in the letter is a sheet I can fill out and return that states I would like to remain on the list for a possible spot (as opposed to accepting another school). The letter also says I can include any information I feel would be beneficial for the waitlist comity to know.

So, what types of things can I send to them that may possibly impress them or help my chances at a spot? All of my achievements were on my applications, so they are already aware of those types of things.