Parchment borders: how to do this? (some guidance pls?)

[bugman]

I'm looking to create a style and theme for my website that looks as if it's written on parchment.

So instead of pixel borders, i would like borders like this: http://www.gorgeousgeorge.com/images...-parchment.jpg

I know how to create the graphic borders and make them look seemless, etc. and i know that they are CSS border "backgrounds" so i know how to implement them on the website.

What i don't know and not sure of is, where/how in the templates styles do i specifiy that "scroll-border-left" will be the left borders on all pages, "scroll-border-top-corner-left" will be the top-left corner of the borders on all pages, "scroll-border-right", "scroll-border-bottom" etc etc

Could someone please direct me on how to do this if documentation already exists or take the time to tell me how to do it?