Sorry for the delay, exam studies and GF had priority, thank you for the comments!
I agree that the execution of the marble effect on the librarian could be better (found it sloppy on some places myself when looking at these pictures), I will go over him again soon and see what I can do to make it look better.
However, while talking about white marble, the colors included in white marble vary with the type and origin of the stone, as some of you may know, some are almost grayscale, others have lots of blue and red/brown streaks in them. Google has alot of good examples, all at a different degree of difficulties to copy. Then again I see why you gave the suggestions you did since when people think marble they see a certain type of it in their mind (which would be the best one to attempt to reproduce for it to be recognized by others and not just be a blurry/dirty piece of armor).
Experience will provide excellens, I'm thinking I won't do any kind of white marble on infantry models for the time being and instead try to get it right on my upcoming white vehicles (on smaller areas to start with). The red marble effect might look good on infantry though, I'll give it a go on my vanguard sergeant (probably) and see what you think.
I hadn't even considered doing a flowing fabric pattern on a dreadnought but now that you mentioned it I might try it out!
I've spent some time to finish of the Rhino, I'm not fantastically pleased with it. When you first look at a Rhino it doesn't feel like it's full of detail and life, but man I was going crazy for a while, finding details I'd forgotten about all the way to the finishingline. I must also admit that I am a noob in the area of weathering vehicles so I did very little on this one. I didn't have the courage to try anything and fail misserably. I'll work up the courage for my upcoming vehicles.
Here's the WIP picture of my Sanguinary Priest
models (they are arm and headless since those parts are going to be white). If you'd like to give me some response on the wing effect I'm trying out it would be very appreciated (middle figure, figures left wing). I didn't want them to have a typical angelic paintjob, but I'm still not sure if it will work:
Also a lonely assault marine (only one left now!):