Bagginsbill made a sand shader some years ago, here is the link:

http://www.renderosity.com/mod/forumpro/showthread.php?message_id=2635530&ebot_calc_page#message_2635530

But perhaps he has some fresh ideas, you have done a great job already.

best regards,

Bopper.

-How can you improve things when you don't make mistakes?