Hi,
I think Joe may have forgotten that he added a very cool feature in 2.3.6.4 which allows you to set a CSS class on the BODY element of a page using the "Page Settings." For instance, If you had a div with a class of header in your layout.master, you could set the CSS Class on a page to header2 and then in your CSS put the following:
body.header2 div.header {background: url('imagename.png') no-repeat 0 0;}
Of course, there will be other CSS rules that will apply to your div but this method will allow you to easily change the header on any CMS pages.
Also, for this to work, the BODY element in your layout.master must look like this:
<body class="pagebody" id="Body" runat="server">
HTH,
Joe D.