hi goldie,
First of all, I'm really not in a position to comment on what the admissions committee/office likes and dislikes because I have no involvement in that process other than giving tours. That being said, maybe you could call and find out. Or stop by if you are from nyc...that would definitely show interest. try to talk to dean brienza, he is a great guy. I can't imagine that they would hold it against you if you sent other letters of rec...but I don't have any concrete answer.
Second, I love NYU...the city is amazing, the student body is talented and fun, and the faculty are very responsive to student needs. I understand it is frustrating to be waitlisted, but it is completely different that being rejected and I'm sure that showing interest doesn't hurt. I guarantee that there will be significant movement. I'll keep my fingers crossed for you.
Best,
Dnt