Thanks for the responses everyone. I am a little confused about some of the talk about using decals. The decals I have dealt with are usually just textures that are projected onto 3D surfaces in the scene. The problem with our engine is that the decal is represented by a single node in space so I have to move that node…
basically you use world position to feed in to the UV's of the line texture, that way its consistent with the world's position, and not the individual mesh, therefore it's much easier to position around. you could make a set of lines in photoshop make them tilable on a seperate tex page and in your normal, stones shader…
You could use splines with rectangular mode on and your decal textures applied. Should be pretty easy to adjust your texture coordinates using this method with real world mapping (if you are a max user that is). Seems like the cheapest and quickest way to me.