For example, can cheerleaders hold a banner at a football game with a scripture reference during a game. Recently that has been a case down in Texas. Cheerleaders are hardly government agents, unlike teachers, and they have free speech and religious liberties. So, I suspect Cheerleaders will be allowed to express themselves as they please, even if it includes religious statements.
However, on an opening prayer, there will be danger is only some (those who say the right types of prayers) are allowed to pray. Cities get in trouble if they give favoritism to those who open city meetings with prayer.