LuckyJoeS on the Hirst Arts ezboard forum pointed out this past HADD competition entry as an example of a fieldstone tower with wooden hoardings on top.
It’s very nice, and similar to what I’d like to build out of balsa wood for the fortress towers. Although I’d like to avoid making it stick out so far over the ramparts and would probably forego a rooftop to make it easier for gaming. Something similar to the upper floors of my incomplete Mordheim Coach House would do. Have to build one for each tower though!