Probably not the advice you are looking for, but a thought. Do you know if you are having a boy or girl? Depending on the sizes of your rooms, you could also put the new baby in the room with the child of the same sex. When pregnant with my second (a girl) we were planning to move my son out of the 'nursery' into the larger room. I painted his new room a sort of tan color planning to decorate with blues & greens. For some reason that escapes my memory, we didn't move him right away, and when baby #3 came along- another girl- we figured there was no point moving him when the other room was bigger & would better hold 2 kids. I was able to keep the walls the same color, just added pink accents. They have never had any sleep issues, my oldest daughter slept right through all the night wakings- in case that is your concern- and I have heard this from other mothers as well, most kids adapt very well to those sounds.
If you are firm in your decision to move your daughter, I agree with the advice to keep the wall color & find some fun curtains to make it more unisex. Also, if you do some searching, you might be able to find bed linens that match as far as design goes, but differ in color for boys & girls.
Good luck on the room & Congrats on the baby!