Creating more visual realistic images in blender is something that I’m slowly getting to grips with, more a case of trail by error at the moment but here's a demo of what I have been trying to get down with some stock images of rust.
At good piece of advice is to apply a high pass filter to the bump map.The image basically consists of a material that has a color. bump and spec reflection map, These 3 are all defined in the texture menu all at once. The only setting is that the color map setting are defualt, bump map Nor was selected (with the NOR and Disp values set to maximum the DISP may not effect the final render), the other setting is the REF or the SPEC make sure that the ref and spec values in the material setting (in the parent top menu are given )
At the moment the final image appears bleached at the moment my only means of getting rid of this is to post process in photo hop using an overlay or a color burn to resurrect osme of the color detail in the final image and applying another high pass final to add some punch to the final render.
The image is saved on home/blender/rustmonkey.blend
monkey: green