I think the answer is a clear no. The ten commandements state that you are only allowed to worship the god of the bible, and that is the promotion of a specific religion. Here is the relevant section.
"I am the Lord thy God, which have brought thee out of the land of Egypt, out of the house of bondage.
Thou shalt have no other gods before me.
Thou shalt not make unto thee any graven image, or any likeness of any thing that is in heaven above, or that is in the earth beneath, or that is in the water under the earth:
Thou shalt not bow down thyself to them, nor serve them: for I the Lord thy God am a jealous God, visiting the iniquity of the fathers upon the children unto the third and fourth generation of them that hate me;"
I agree the answer is a clear no. I believe this is especially true as a permanent fixture.
However, in my home town they used to (perhaps still do) display a nativity scene on the court house lawn at Christmas. I don't mind this sort of thing since other religions can display thier scene on their day. At least they could where I lived. We never had those displays at schools.