If you are looking to enhance the skin textures to some level of realism, I would suggest you take a look at this thread:

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

It is a system which includes a skin shader template created by Bagginsbill and available for free.  It is capable of taking the most mediocre texture and convert it to something as close to realistic as possible. 

I would also suggest searching and reading any thread posted by Bagginsbill dealing with the subject of gamma correction in Poser and its impact on renders and image quality.