There are some disgustingly elegant and absolutely
methods of faking the marbeling once used
in traditional book flyleafs and still of intense interest
by scrapbook enthuasiasts.
They also open doors to new and horribly efficient
methods of doing all sorts of computer synthesized
artwork that does not at all look like in the least
that it was done on a computer.
Many thanks to Robert Ackerman for his valuable
insights and many coding examples.
More variants here.. Your input welcome.