I realize that is kind of a trivial suggestion. I am just dropping it here. Not important if it is ignored or not.
A door creaking sound would be really good to have especially on siege. Suppose that the guy below is an attacker and secretly infiltrated the gate tower ninja style. He is trying to watch the open end while he constantly has to check his back to see if a defender suddenly appears behind him. I know we have the tilde key and stuff. But it would still be cool to be able to hear the door creaking behind you if that happened.
And here are some sound effect examples:
http://www.soundjay.com/door-sounds-1.html The website info even says anyone is free to use them in their projects free of charge (haven't read the entire terms&conditions though).
Again, I would like to repeat this is essentially a trivial suggestion. Up to you guys to totally ignore or support it.