I have made the stone a bit more matte and fixed a bug in the texture generator. The bug was causing some warping, stopping stuff from fitting nicely.
I have been experimenting with different strengths of my current procedural detail-adder, but I think I should try to create a more rock-like procedure.
Procedural detail strength = 0.15:
Procedural detail strength = 0.5:
The lower strength gives a clearer image, but the higher strength looks more rocky. I'll be going with 0.15 for now, but I will reevaluate this when I have added some depth cues and created a more rock-like procedure.