Pete, check out cool_kettle.jpg in my home directory.     
I started with a graphic I rendered with povray.  I cut out the kettle
superbly using the bezier select tool, inverted the selection, filled to
black, inverted selection again, cropped the kettle, greyscaled it.
then I took dendrite.gif, blurred it to un-GIFify it, scaled it to the size
of the kettle, duplicated it and cleared the duplicated image to black.
Then I did a composite of the dendrite & black image using the kettle as
the mask.  Then I blended that result with the greyscale kettle.  Then
I added the result of the previous composite to the result.  

It looks like it was painted with laser light.  neat FX!
