I decided to turn light up in my game and take some screenies:
http://hotimg8.fotki.com/a/12_218/95_201/ScreenShot-227.jpg
http://hotimg19.fotki.com/a/12_218/95_201/ScreenShot-228.jpg
http://hotimg16.fotki.com/a/12_218/95_201/ScreenShot-229.jpg
http://hotimg25.fotki.com/a/12_218/95_201/ScreenShot-230.jpg
http://hotimg8.fotki.com/a/12_218/95_201/ScreenShot-227.jpg
http://hotimg19.fotki.com/a/12_218/95_201/ScreenShot-228.jpg
http://hotimg16.fotki.com/a/12_218/95_201/ScreenShot-229.jpg
http://hotimg25.fotki.com/a/12_218/95_201/ScreenShot-230.jpg
Physics is an important thing to consider when placing rubble, rocks, etc. Think about the weight of each object for example. A large, heavy boulder wouldn't just hit the ground there and stop on top of it. It'd probably crack the ground underneath it, sinking in a little, or even a lot in some cases. You should retexture the imperial rubble ring and imperial block to make velothi versions, then have them sticking out of piles of rock here and there, or just out from underneath a fallen boulder to simulate pieces of the floor/ceiling/wall breaking apart. And add lots of little, smaller rocks around the bigger ones, because when the larger pieces broke free from the solid rock, lots of smaller debris would've been dislodged as well.
Also, you can use the dwemer ash pile as dust/dirt piles and mix them in with the boulders as well, as there's probably a mixture of sand/silt above the rock layers, since there's a seabed above, and lots of sand would naturally fall through the cracks in the rock layer and spill out where large portions broke away.