Teams often struggle with creating a Mission Statement. Too much over-think it, analysing every word and trying to cover every corner case. It shouldn't be that difficult.
As I went from an Associate Engineer title to Senior Director, I kept the same (personal) mission statement: "Get chips out the door." At some point I changed it to "Get product out the door" but the sentiment was the same. Anything I was working on that didn't help get product to market was time wasted.
When you work on your mission statement keep it simple, keep it grand -- and make sure it align's with your boss's mission statement! Make sure you are communicating it to your stakeholders and your employees every opportunity you get. Align your day, every day, towards your mission statement.
Don't over think it -- but do think big! Figure out what what has to happen to make your mission come to life. Think big. My vision was that our IT team would be fully integrated into our customer base. That didn't mean my team would try to design chips, it meant they would use their technical skills to enable engineering to be more effective and efficient. My vision was that we were a customer service team first, a technology team second.
At every turn I made sure we were solving real customer problems. There were times that we had some great technology from the vendors looking for a solution that never made it into production, and as a tech-geek that would make me sad, but there were plenty of real problems that needed solving first.