pemberaidembetembe

Hi Im a final year architecture student doing my dissertation on an archaeological site. I've modeled the ruins in ArchiCAD and renders in Artlantis, but cannot get the textures to look "dirty" and old. My supervisors say it looks wrapped in wallpaper!!! How do i achieve rustic brick and dust?? Any good examples out there of 3D ruins would help!!! thanks Software: ArchiCAD, Artlantis, Revit, Sketchup, Photoshop, 3D Studio max Cinema4D(still learning it)