This is for the people who are having troubles playing siege battles in custom battles (with pictures!:surprise:):
FOLLOW THESE INSTRUCTIONS EXACTLY!
1. Select a map without the little silver box next to it.
2. Set the settlement level to "Fort"
3. Select your culture (such as Empire)
4. Re-select your settlement level (such as Huge-City)
5. Play the siege battle!
Have an enjoyable siege!:thumbsup2