I have some more suggestions:
siege equipment:siege tower (you can put units in it and it will move towards a castle and once it gets to the castle it drops a board which units walk across it and get onto the castle)
ballista (shoots huge bolts and once it hits a soldier it shoots the soldier back and the enemys behind that get stabbed and stick to the bolt.so basically it turns soldiers into shishkababs)special units:
zombie (when it kills someone the person it killed will turn into a zombie and they turn after 3 secs and if the zombie killed someone with armour/weapons they keep them)
zombie necromancer (spawns 4 zombies around it in a circle and shoots bolts that when kill a unit it turns into a zombie and has a special ability that pulls the life out of enemy troops,turning them into zombies in a large radius)
skeleton ( a bit stronger then a zombie and can spawn with armour/weapons and when it kills someone it takes the skeleton out of the person it killed,turning the enemy into a skeleton and they keep there armour/weapons)
skeleton necromancer (summons 4 skeletons around it in a circle and shoots bolts that kill enemys and turn them into skeletons,and has a special ability that pulls the skeletons out of enemys in a large radius)
can you add insides to castle walls? if so please do as that would be really cool and add slots so you could put cannons in them.thats all I got for now hope you like them JNI.