Very interesting and informative post! Not to muddy the water further, but here is a quick render I did to illustrate an idea I had for simulating a burning torch. I used a free rockwall texture set from the PhotoSculpt site. The application uses two photographs taken twenty degrees apart to generate its texture maps. There are 10 free sets of maps available for download.The sets all have diffuse, ambient occlusion, specular, depth(displacement), and normal maps. The wall is a simple plane primitive. I rendered this in C7Pro, so I'll have to fire up my other computer with C8Pro to try the normal maps.

The PhotoSculpt app itself looks very interesting, and in addition to generating all those maps can make a 3d mesh to go with them. http://www.photosculpt.net/ I intend to try the demo when I get a new higher rez digital camera.