This is my second SM map. I made this one in a couple hours (still with my cousin), and it worked out great.
It's played on castle ramparts above a sea of offzone. The ramparts rise from the spawns at the edge to the pole in the center. It's quarter-symmetrical, and there are quite a couple of possible routes, but it still takes about 30-40 seconds to get to the pole from any spawn. We tried to make it take the same amount of time from all of them, with about 5 second differences at most. Their priorities are set to avoid players spawning next to each other when it's not necessary.
If you add it to your server, please let me know here, I'd love to check it out online!
Good luck, have fun!