There should be a built-in script for converting gamma values to select material like PoserPro.  Unfortunately, IIRC, it is not selective how to apply it to nodes, but I'm just assuming because I never use the feature before.  In situations where is bump, normal, displacement maps are absent, I generate my own in either Photoshop, Gimp, or ShadowMap.  Generally, many material zones share the same image maps and node structures, and if you modify one, you could copy and paste into another.