Bagginsbill has created the most versatile shader system that adds stark realism to just about any skin texture available.  It's application can be extended to other textures with modifications, but the best thing about it is, that it is free.  The link below will introduce you to it's development.  It is an extensive read, but there are plenty of examples and comments.

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2737823&page=1

Welcome to the mad world of Poser where every render is like stepping through the wonder mirror.