Most sieges are basically beating the heck out the the Ballistas and Archers in the towers with a long range weapon like a Trebuchet so you can finally get your army in the walls. I wanted to go for a different type of siege, so I constructed this Invasion map where small bands of enemies harass your attempts to siege the combined forces of all 4 baddies. The design is nothing special, but the four colors of the enemies and their flags and etc. look kind of cool.
I've made hundreds of maps and never submitted one before because they were all designs I liked but none really had an original concept. I'm sure this scenario has been attempted before by someone, small bands of attackers while you siege a castle, but here's my take. The other thing is, I didn't put in tricks like pitch ditchs and spikes. Instead, I put small groups of defenders throughout the castle and you have to battle each in turn to get through. I also left out the massive banks of Archers and Ballistas that decimate your troops before you can even get to the walls.
This scenario has a more hand-to-hand combat feel. Your home Castle is pretty well situated and defended and there is little danger to your Lord, a home castle is included so you have a continuing source of recruits- the main thrust of this scenario is including enemy reinforcements to upset your siege plans, with increasing numbers and occurances until you are overwhelmed and unable to mount a decent attack on the enemy before time runs out. You have nearly unlimited money, food and weapons, so you can concentrate on military strategy.
I included 4 points of entry topographically, although I removed the Signposts nearest the base Castle so the invaders would focus on the siege parties. These could be re-added and the Invasions tweaked to make a more traditional Invasion Scenario for this map.