How would the team act toward each other?
Don't be too specific, you will limit your vision and it won't be applicable five years down the road: for example, if your current goal is to expand and move into a larger building, that's a vision for the future but it's not the vision for the future of your entire business.
Everybody needs to have a say and feel a sense of ownership. You see God and Adam's fingers very close—almost touching. Since the vision statement isn't just a vision of your future - it's also a vision you're presenting to your customers about who you are - it's important that it do just that. But above all, a vision statement must be compelling, not just to the high-level executives of your company, but to all employees.
Keep going until all members have shared all of the ideas they wrote down in the assignment. What's your purpose? The best statement will be clear about who you are as a company as well as who you wish to become.
Use clear, concise, jargon-free language.