I think there is an excellent selection of community buildings. People can add to the list, but here are some of the suggestions I have for future community buildings. (Not all of them have to be high levels):

1. Airport - It would a nice addition to any city.
2. Seaport - A city on the water needs one for interstate commerce.
3. Football Stadium - You got one for baseball, why not have a football stadium (gem purchase required)?
4. City Marina - A city on the water requires a place for people to dock their boats.
5. Speedway - Just another day at the races. (Doesn't matter if it is Indy stock car or NASCAR and just like the baseball stadium it does not have to discern one way or the other)
6. State House - We have the city building and the courthouse, why not have a state capitol building where decisions are made? You could incorporate possible future quests with this building, but you don't have to.
7. Jail - I know, not positive, but just as you have a police station in a city, there will also be a county lock up for those that are not so great.
8. Middle/High School - For those that advance beyond a 5th grade education.
9. University/College - For those in the city that wish to expand their education or it may draw in other students from elsewhere. (with a frat house in the town, this only makes sense)
10. City Zoo - For the wildlife of the city. (potential gem purchase requirement)

Just some ideas for future community buildings.