Thanks guys!
I definitely plan a palette edit, good thing to have the job laid out for me

The present palette was well suited to the first version, but I agree it doesn't work all so well with the bg changes.
The colors were actually picked from Boecklin's paintings (such as they are displayed on Wikipedia, see link in 1st post) and these show either dusk or daylight, not night. I'll stick to a sunset/dusk kind of light if I can.
I agree the volume of the topmost part looks low again. I'm not sure why, since I made it obvious that the ground rises sharply before coming to this plateau, but I'm going to live with it at this point. I wanted that flat space as an arena for some of the monuments (yet to come), and also to provide eye-resting space from the more intricate gully parts.
New update hopefully later tonight.