I just tried a small experiment in P6 (same thing happened in P5)...

I copied a texture (selected at random)  from its original folder to the desktop. The I fired up Poser, loaded a cube and applied the texture (from the desktop) to the cube. The texture showed up in the preview.
Then I minimised Poser and re-named the texture on the desktop to be different. Restored Poser.
Moved the camera around in the Preview (Pose Room) - there was no problem - texture showed up fine in all views.

Hit render (Firefly), and guess what? It couldn't find the texture (and came up with a dialogue complaining about it).

Conclusion? Even tho Poser still has that texture sitting in memory (it must have, otherwise the preview changes wouldn't have worked), Firerfly reloads textures from disk..

Which leads to the inescapable conclusion: Every (bitmap-type) texture that you apply to anything gets re-loaded (thus duplicated) at render time....

(Not sure if this applies to the P4 renderer, that's for another experiment..)

No wonder Poser uses up memory fast...- consider all those 4096x4096 V3 textures being duplicated...

Umm. One thing I didn't do which I should have, was check that the preview mode still worked after the attempted (and failed) render. Oh, well - next time...

Cheers,
Diolma