Took a picture of a cobblestone sidewalk and treated it to be tileable. Package includes PSD with diffuse texture, normal map and a scene with the material shown.
The PSD file also has an invisible layer with the accompanying normal map (for safety, iincase the normal is lost or something), another invisible layer with a heightmap if needed. Also, the PSD has an alpha channel embeded so that the specular shaders... speculate the right way (meaning no speculars in the dirt.)

*Tileable
*Diffuse + normal
*Alpha channel in PSD for proper highlights in Unity's spec shaders.