URL is www.theresasheridan.com/blog

Right now, I have the background set up with the actual header image, which is full width. Then I have a fixed width content and I have put a padding at the top, so that it will drop below the background header image.

What I want to do is add a repeating background below the header image, so that it resembles my main site at www.theresasheridan.com.

I had tried a fix I found at http://letusbuzz.com/2011/03/full-wi...-in-atahualpa/, and this works, but it doesn't allow me to have the menu over the header image, as I do now.

How can I accomplish this, or can I?

You might be able to style the html tag with a background.

You've kinda lost me, which HTML tag are you referring to? The body already has the header as the background.
If I wanted to add another wrapper div, how would I do that? Then I could use the wrapper div for one background and the body for the other....at least I think I could. That's how I did it on my main site.

Something like this with the proper CSS perhaps

html {
background: url(/wp-content/themes/atahualpa367/images/backgr.gif) repeat bottom left;
}

You're using the Ultimatum theme framework?

Probably wasn't using Ultimatum at the time of the original post.