> Another question: since I'm supplying a PNG copyright to be overlaid on top
> of my image, I assume someone will be recompressing it.

	Why?  PNG uses a lossless compression scheme, so if you tell your
graphics application to use the maximum compression (this is typically a
value of 9 for PNG) then you'll get the smallest* filesize for the exact
same quality.  Simply it's slightly longer for the app to write the file
(and also to read it again), but on nowadays computers it's lighting
fast, especially compared to a POV-Ray rendering  :-)
	POV-Ray has no such setting, as it always compresses PNG with the
maximum possible compression with respect to how it renders its images
i.e. line by line**.

(*) in fact not always, other softwares are sometimes able to recompress
slightly more some PNG images that were saved with the maximum compression.
For instance: http://pmt.sourceforge.net/pngcrush/

(**) therefore the (*) above might be worth the try with an image created
by POV-Ray, as such extra tools will compress the file based on the whole
image data instead.

	- NC