This script quickly adds a "plastic wrap" effect on all layers in an image. The preview image is just a plastic wrapped version of the lava animation preview:
The plastic wrap is a GIMP version of the PS filter and was created by newt and discussed here: http://guicon.110mb.com/?Scripts:Plasti-Wrap
The script at that location works on a single layer; mine, all layers.You can download the script here-> FP's plastic wrap all layers script
Download the zip file, open the zip file by double-clicking on it and copy/paste the script to your GIMP scripts folder (ie...C:\Program Files\GIMP-2.0\share\gimp\2.0\scripts). Refresh your scripts and you're ready to go. The script can be located under the Filters > Light and Shadow > Plastic Wrap All Layers... The lower number you use, the more plastic added.
Let me know if you have any trouble or need additional information.