PALE MARBLE
Start with a nice even white undercoat, I suggest you use a spray as it will avoid any brush strokes showing up. On top of this apply a couple of thin coats of bleached bone. Now thin down some snakebite leather and paint on some jagged, uneven wide lines for the cracks. Try to keep these going mostly in the same direction for now, although having a few of them joined by a line in the other direction is a good idea, we’ll get a bit crazier a little later
try to get the edges of the snakebite lines to blend into the base colour a bit. Using nice thin paint helps with this.
Fill the centre of these lines with a line of crimson gore (not too much precision needed here),
then add a bit of black to the areas you want to appear as deep cracks (less is more!)
Now we vary the colours between the cracks a bit. Take some thinned bleached bone/skull and paint it onto some of the bleached bone areas, again trying to blend the edges into the base.
Then do the same with pure skull white. Filling in the area between some of the cracks with pure white creates a nifty look.
If you’re feeling particularly squirrelly you could add a few darker patches using the process above with a bleached bone/graveyard earth mix, but it looks fine without.