Nice, I like it.
I also modified my Barad-dur:
I replaced the visible light and dark grey bricks in the 2nd and 3rd floor with black ones and increased the height by six bricks.
I am considering adding a couple more bricks of height (which would allow me to work out the details/textures I added a bit better) and replacing the grey slopes atop the front gate with black ones. Also, I might change the throne room roof like you did :-)
What do you think?
Also, are there any examples of Orthancs with increased height? Orthanc looks like it got squished a bit, too thick/too short. But aside from that, it is great esecially in combination with Barad-dur.