I would include the coaches name, the name of the team and division, the season/year he/she coached, and if there is some saying or motto that the coaches use.
What sport is it? You could go with a famous quote for that sport or from another coach.
I would go with something that could be displayed in a home or office without being overly trophy-like. Most plaques and such like that are really only displayed for a year or two. The others are kept around a lot longer. I'm just saying this from experience of a household of coaches and teachers
When I was "team mom" for my son's football team, I bought them clocks and just had the year and team name engraved. I also gave them each gift cards to local restaurants.