One thing bothers me here. It is the way that in one breath we cry for the first ammendment to protect free speech and then in the next breath use it to quash the religious principles and heritage that founded this great country. If a large erotic (but not pornographic) mural were donated and put up in a public building, those crying for its removal would be labeled as anti-american because they want to tread on the first ammendment protection of freedom of speech. Yet, if a large mural of something stated to be religious is put up, those same people who look down on others for treading freedom of speech turn around and cry that this isn't freedom of speech, but a government endorsement of religion.
A religion does not have to be formal or formally recognized. Webster's first definition of religion is, "a set of beliefs concerning the cause, nature, and purpose of the universe, esp. when considered as the creation of a superhuman agency or agencies, usu. involving devotional and ritual observances, and often containing a moral code for the conduct of human affairs." So, let's see. If I believe that the world was created naturally, through physical and evolutionary processes, that the purpose of the universe is for me to simply live in it, that humans evolved like all other animals and developed their own intelligence and agency, then I go out and plan a weekly hunting or fishing trip that can be seen as a ritual to nature, and create a moral code for the conduct of human affairs in nature (such as don't litter, don't kill what you can't eat, don't destroy nature), then I would have all the necessary points to be considered a religion. We'll call it the Church of Nature (I don't know if there is a body named as such, and if there is I mean no offense). Now, as a member of the Church of Nature, I paint a beautiful scene of mountains and forests and streams. Can that picture be put up in a government building since it is an affirmation of my religion and beliefs? What if I also add to the bottom, don't litter, don't kill what you can't eat, don't destroy nature?
This example is a little extreme, but it was to make a point. Will we get to the point where everything is somehow religious or offensive to somebody? What then? Will there be no decorations, no murals, no pictures of any kind? Where does it end?
The best solution is to first minimize the amount of land and property that government "owns" in this country. Government should not "own" land because that simply means that it is owned by all citizens equally. And unless all citizens have the same opinions, then all citizens should not own the same piece of property, as there will be continual squabbles over it. If everything is owned privately, then this whole problem is circumvented.