Gravity Guru
Just a quick kind of half serious stone texture I did tonight. I do plan to work more on this so any tips would be appreciated.
Nice start. I would next splatter a light gray over the whole thing (I normally use an old toothbrush to flick the paint) and then do that again with a white paint.

Next, I would create some highlights along one edge of the cracks to add a bit of dimension.
I pull the trigger back with no air then give a burst of air for my splatters. You can also choke off the hose or spray on to a clothespin or something.
Also referencing stone pics helps. Many kinds don't have lines but maybe a few cracks. They also typically go in the same direction, but not always. I prefer less lines unless I'm looking for a busted up look. Pick a light source and add highlights to that side of the cracks. Will really make them pop.
I would use at least 3 greys for splatters, one very light, a middle and a dark, and as has already been said, highlights along the edge of the cracks.
Thanks guys. Looking at this again, I did get carried away on the cracks. Just practice. I won't do so many on the real project.