Fantastic model there Steve. You are like me and love to get the detail right.
Image maps are a good idea though I also tend to mix those along with procedurals also using several plugins from "Digital Carvers Guild" such as "Anything Goos" and "EnhanceC" etc and then bake the produrals to create the remaining image maps.

BTW.. Was the model built within Carrara or did you use an external modeller?