There's no rule as far as I am aware of that has you bar pictures from any people on your user pages. So you can post whatever, or whoever you want, but as long as it doesn't break the Terms of Use.
But a general rule on the Internet, don't post/discuss politics (or religion, or sometimes even sports) on a site not dedicated to it. Because it will create more problems than it will solve and doesn't really add anything to anyone's enjoyment of a franchise.
