3) Break up the sight line a little bit. I think a fence or two in the picture below would really improve the flow. Block the direct line of sight into spawn with a fence. This doesn't actually cripple defense, instead it gives soldiers and demos a nice ledge to dance around on .
Went back and looked through your earlier pics, looks like i'm not the only one who suggested you place cover here.
Why are these bad, they seem to be breaking up your big grey walls pretty well.
One of the things that i found curious is that this always seemed like a mine or quarry to me, the caves themselves appear carved out, so the stalagmites/tites seem nonesesical if this was man made. If it's a natural cave you generally don't see trusses supporting the cave. The contrast of mines vs caves is jarring.
The second image pair you have on your OP seems the more natural, a natural cave with natural geological formations boken into by a mine passageway; Except stalagmites continue to litter the rest of the caves as well (in the player space) that seem more man made because of the trusses and less eroded, square shape of the tunnels.
The reason for the image paintover i uploaded was because i've visited similar caves like this in Wales, including but not limited to "Dan-yr-Ogof".
http://www.gower-view.co.uk/dan yr ogof.jpg-for-web-normal.jpg
http://www.showcaves.co.uk/Images/cathedralcave.jpg
http://farm5.static.flickr.com/4074/4942692427_ec442a4af9.jpg
http://www.t-bones.co.uk/wp-content/uploads/2011/03/IMG_3715.jpg
http://www.4winmobile.com/tg/Xda_Ignito/IMAGE_026.jpg
None of these locations have trusses, caves like this can support themselves so i feel you need to define what's been quarried out and what's a natural cave and keep the trusses to one location and stalagtites/mites to the others (whilst nothing is preventing you from sticking your unique rocks in both areas).
I also marked out a path because the ground blend seems almost entirely the logical response to breaking the color monotony at displacement seems, whilst not entirely adhering to the notion that paths/foot erosion get marked out by people traffic, i feel some of your ground blends within the cave are not totally realistic in execution but the direct response to color theory. This feels less of an issue for man made tunnels as the geology is different (you get more rubble, as seen in mine based scenario's like dustbowl/goldrush). Unless you had some crates or man made objects that would demonstrate an area getting used by people, some of the ground blends seem off.