Not in front of poser, so the naming might be off.

 

Select the clothes item. Open the material tab. In the library also select the material area (far right). Navigate to the folder you want to save it into or create a new folder. Look at the bottom of the library window. when you are where you want to save the file, click on the plus sign and save as a materail collection and select them items of the clothes for your new texture. Click OK or save or whatever and this will create a  .mc6 file. In P8 and PP2010 you can now place that file into your pose directory and it will behave as a pz2 file even if it has the mc6 extension. If you want a nice looking icon, that you will have to render yourself.

 

You can't save a texture directly into the pose part of the library. You have to save it to the material section of the library first

Gary

"Those who lose themselves in a passion lose less than those who lose their passion"