"As you discuss this remember that Poser 4 had some very strange things with it. Thumbnails were in a non-standard format as were bump maps. There are probably a whole host of similar gotcha's." 

The old standard icon were in RSR format which still exit in many early content.  IIRC, only Poser 7 was able to read that and the newer PNG format.  And yes, bump maps had to be in .bum format and plugged into an entirely different node connection.

I believe Poser 7 was the last version that could read it. Poser Pro (Poser 4.5) was the first Poser that used PNG for thumbnails, but Poser Pro through Poser 7 could read them. Those are just two things that I recall, off the top of my head that keeps people from just using content that was not designed for Poser 4.