We have a background image that scrolls continuously up the page in a loop. You can see it here:

http://aesajewelry.com/staging-site/

The client not only wants that, but she wants it to move from left to right in a sinewy movement a bit like an 's' as it rises.

I assume this requires some knowledge of math and sine curves or something like that that I have no idea about. Could anyone point me in the right direction?

I wouldn't need the image to repeat-fill in on the left and right as it moved out of the div - I can just fill with black for that.

Thanks.

Pat