My town is (I'm pretty sure) the only town in the United States that has the Ten Commandments posted in the courthouse. The reason they were able to? They posted it alongside the Magna Carta, Constitution, Hammurabi's Code, the Mayflower Compact, and a few other documents which are there to show the basis of laws.
I don't see a problem with the Ten Commandments being displayed in public. Most of them are rule EVERYONE should live by, no matter what your religion. Sure there are a couple that non-Christians don't have to pay attention to, but everyone should be living by the rule of "Thou shall not kill," and the others.
Besides, it's not really the issue of whether they can be displayed in public, as much as whether they can be displayed in government buildings. Heck, there's a building in my town that has the Ten Commandments in a huge sign on the side of the building. About 98% of the buildings in this county have the Ten Commandments in them somewhere, despite the large amount of non-Christians who live here. Nobody seems to really have a problem with it.