Ahh nice, more suggestions to put up !
Please considerer to have BOTH variations available !!!
Having visit a considerable amount of castles over the last 50 or so years, there is ample scope for both full stonework, but as least as many places where it would just be cornerstoning and framing being visible on the vertical planes of towers and walls, whereas the rest would be "plastered" (both from esthetic and military reasons!)
In consideration with your picture....
the front-part (with the door) with full stonework is nice
the left-part (with just the windows) would be what I would probably opt for for my towers.......
having both available as an option would be nice
ps. the crenelations would be visible stonework in all cases, so texture away there !!!
pps. the flooring for the fighting deck of the tower could be both stonework or wood! in either case, it would tend to be slightly dome shaped and have "holes" a;;owing excess water to flow down the side of the tower....