I can only give my opinion, but for what it is worth here it is.
I was a teacher until I decided to stay home when I had my first baby. I was always appreciative of everything that I was given. I thought that it was great that the families went to the time and expense to do something nice for me.
I would say no more MUGS, no more CANDLES, no more BATH and BODY products, and absolutely no more FIGURINES. One can only have so many mugs, some people like me don't care for candles or are allergic to the different scents. Some people don't care for bath and body stuff (like me). I think that I (and others) have a slight allergy to the different scents. More figurines means more dusting. With that said, if you know for sure that the teacher loves one of the ideas listed above then by all means go ahead (for instance if you know that someone loves Party Lite).
My favorite things to receive as a teacher were notes of appreciation. Nothing can top the feeling of being appreciated. After all, a teacher spends more time in the presence of a child than most parents, and it is nice to know that the parents recognize the importance of you in their child's life. As far as material things go, I would shoot for gift certificates (favorite restaurant, teacher supply store, mall, etc). I happened to like getting ornaments. I never took them home because my tree has a theme, but I would put all of the ornaments that I collected over the years on a tree in my classroom every year (of course I had the child's name and year on it somewhere).