That second tower, with the smaller annex to it . . . Not sure how to best play it in a battle. You could either simply allow the entire castle to function as one, with more available defenders and more available assailants. Or you could treat the main tower as the main castle, and the smaller part as something that can be assailed separately (fewer models attacking, fewer defending), which, if taken, can then join in on the assault against the main tower.
I'm also looking at ways to creatively incorporate both towers . . . maybe with a "bridge" between them, forming the only place at which one army can ford a river and join the battle taking place on the other side of the table.
Any other cool ideas?