To derive a particle product you need:
1. to create one texture image with 128x128 or 256x256 pixels sizes .png format.
2. the file MUST BE NAMED EXACTLY particle.png
3. to apply the texture to the product on create mode in IMVU client
4. to place your particle.png in the assets folder. The folder is located above the avatar. Then press apply changes.
5. to save and submit your product to the catalog.