i really don’t know how to explain it in a more simplified way than to just design your background in illustrator like i do mine. i’m horrible at technical instruction and any time i share something like that on the blog, i get about 300 “i’m confused” emails (i still get emails daily about streamlining photo width). unfortunately i just don’t have the time or resources to help everyone. it’s easiest (for me at least) in illustrator. you just put the scallops on the side, export and upload to an image host. i’ll search google in a bit and see if i can’t find a decent tutorial on how to do it. :) though i’m sure if you just search “how to make background image” then you’d find some useful tuts.