Looking kinda horrible to me, but I think it's fine for the last stand =)
Structures:
1. A jolly good spot for catapult. Enemy archer might having a hard time to shoot it.
2. Trap bridges: Good for hit and run attack, (ninja!) stick your head out, bomb them, shoot them, do whatever you want then run back and hide.
3. Trap door: If you know what I mean, just destroy the bottom of the main door and the rest (the 2 door sticking out) will fall on the enemy.
4. Stone base: Just a little thing to slow down tunneler
5. Bunker: It's good to have an archer lurking there.