How makey "wrap around" bg/banner in blogger?

First, my advice from before is useless b/c you already have "fixed" as one of the attributes for the background image.

Your image has a "center" attribute which is why it's moving when you resize the window.  It keeps trying to center itself.  Also, I think the "fixed" attribute is keeping it from scrolling up and down with the rest of the content.

Does blogger let you edit the css files?  Wordpress doesn't in their free version but you can pay for the privilege.  If you are constrained to a few built-in options that come w/ blogger you may be screwed.  If you can edit css (or override the defaults) you have options.

I would try setting the image absolutely which is usually done by describing the position in css for the top left hand corner of the image. If you wanted the picture at the very top and 100 pixels from the left of the window it would look like:

body {
  background: url("link to your picture here");
  position: absolute;
  top: 0;
  left: 100px;
}

or you can float the image which means that if nothing is in it's way it will display to the left or right side of the screen or whatever containing element it is inside of. In your case I would try floating left and adding padding to the picture to position it which would look like:

body {
  background: url("link to your picture here");
  padding-left: 100px;
  float: left;
}

I am by no means a CSS pro. I just learn enough to get what I need done which means lots of stumbling around. It generally gets the job done w/ some perseverance.

FWIW- Like many people I use the firebug extension with firefox to figure out what's going on.  It lets you click on an element on your page and tells you what rules are being applied to it.  It takes a bit to get used to using it but is fantastic for troubleshooting.  I also refer to the sitepoint css & html reference constantly to refresh my memory on what tags/attributes to use.
Hope this helps...