Verlinden makes a courtyard type structure that has the remains of a tower and wall with it they also make extra wall sections for it. As for reference pictures you can try the book Tigers at the Front, It has several interesting photos of vehicles in repair. One of my favorites is a three legged winch with wood legs from rough hun tree limbs in an attempt to lift part of the engine, in the background of the pic. you can see the twisted metal legs of the winch. As for people you can try verlinden, Warriors, or Dragon. Verlinden makes several mechanics and tool sets that have served me well in past dioramas. If I can come up with other books I'll let you know.