I know. It's a broken link, because your header template is calling the wrong folder for the image. That link is what your site is putting out, hence the red X.[/quote]
And that should do it. Just search in the header template for banner.jpg and it will bring you right to the bit you need to edit. Or (easier) just copy banner.jpg into the misc folder. I'm betting that all of the other style problems that aren't showing the banner are the same reason. $stylevar[imgdir_misc] points to /images/misc/ under the name of the current style. So if your style is installed in the /leaf/ folder, it's looking in /leaf/images/misc/.
Also, please wrap your code in [ code ] [ /code ] tags when you post it up here. Makes it a lot easier to read.