As you can see, there are subtle, far and few (in relation to other bump maps) bumps and ridges, displacements on the sides of the body. Is there a way to achieve these sharper ridges without manually doing this? Perhaps there’s some modifier that displaces the sides at random, with a value you can set for how sharp, how often, and how close these displacements are.
You can feed a black and white image (or even a noise texture) through an RGB curve node containing a curve with one or more sharp transitions or points (as opposed to smooth transitions). Then you would plug it into the displacement output or the per-shader bumpmap input like normal.
If you have clear photo of the area you could use Gimp to make bump or normal map then use it
i have NEVER had good results using a black and white copy of a SHADED relief color image as a bump map
a shaded relief image – is not a height map and never will – , this is a bit of a pet peeve of mine after correcting the hundredth person to try to pass off a B&W copy of a texture AS !!! A HEIGHT MAP!!!
if you do not NEED!! the actual dings and dents in that above image
use some noise and make a light noise displacement map
dings are EASY single mouse clicks with a paint brush
scrapes are just lines
now if you NEED those exact dings and scrapes …
That is a bit harder
Shape from Shade
– a quick one gives me this 8 bit copy of the 32 bit float – just the left panel only
I would try a couple of differently scaled noises, musgraves, or combo of these - multiplied you’d get small scale bumps only where the large scale map is high in value. Maybe even blended with a hand painted mask to limit that even more to only show up well in the central parts of the panels.
If using bitmap textures, I’d try to model it and grab normal maps. I wouldn’t expect bitmaps to work well as bump maps due limited depth.