I found this image (and the links below) while searching cyberspace for artistic mossy rocks. If you have time you should download Unity3d and take a lovely simulated walk in the countryside.
Once again it seems dry stone walls can add so much, not just to real property, but even virtual reality.
Anyway, here is what they say about it....
"Give your terrain that touch of authenticity with this beautiful, rugged dry stone wall. Use it with or without leafy vines. Works great in a variety of settings, from lush green countryside to bleak forbidding landscape.
* Six modular wall sections: small, medium and large, each plain or with vines.
* Two LOD levels for each mesh.
* Materials with high res textures using diffuse and normal maps.
* Prefabs for each wall section, with collision.
* A demo scene is also included.
See an example of the dry stone wall in use at Summer's Day interactive landscape. (Press Shift for “instant travel” and click on the Ivy Walk icon.)