It sounds like you are trying to represent levels of texture in multiple images.
It depends on the actual surface texture you are wanting to portray. but I would think you could simply adjust the intensity of your bump map to raise or lower your texture.
If you don’t need an actual 3D representation of the texture on the surface of the object, you could simply take your texture at it’s roughest level into Photoshop, duplicate it with a solid color layer behind it that matches the tone of your texture, and adjust the top layer rough texture’s transparency to generate multiple copies of the texture that vary from soft to rough.
You could then generate bump maps from these textures of varying roughness.
I am not a pro at materials, but maybe these ideas will help.