We can't tell you for sure, because none of us are lawyers that I know of.
From what I understand, anything "State and government" we are able to use. The reason (from what I've heard) is that we pay for that stuff in our taxes. It's bought and paid for by us.
Pictures from Nasa for example, I do know you can use. I've been on that website and downloaded some pics of the moon and it says is their Usage disclaimer that you can use it.
Your City may be incorporated as a business and that may make a difference. I'm not sure.
D