The stone texture I made uses similar techniques to the metal texture above.

 

Basically, I found an image from the internet of a brick wall that didn't tile. I then blocked out the image in Maya by creating cubes over the image plane.

 

Next I exported the blocks to ZBrush to sculpt detail into each individual brick. I then used xNormal to bake the normal, occlusion and covexity maps from the high poly bricks I made in ZBrush. And painted the diffuse map from these in Photoshop. The gloss and spec maps were created by using filters in Photoshop.

 

Finally, I applied all the maps to a single plane for the final render.