She and I use Wings 3d, although I also have used Milkshape.
I like how the guard tower turned out. Even the windmill looks great. The idea of a gate-bridge was what drew us in. The little details like that get us interested.
Perhaps some added models to your pack would be items like a stable, catapult, some various items such as a pitch fork, water trough for the animals to drink out of, a water pump (the old-style hand pump), a cannon or some other items for defense, etc. Then you have a medieval pack where people could build their little castle and have the necessities to start with. Just ideas...
Cheers
Mike