Note that you do not have the same HTML/CSS power in emails that you have on a Web page. For example, Outlook a few years ago became somewhat primitive when Microsoft chose to use the Word engine to display HTML. So, you cannot rely upon background images in your email. I believe you can use them in table cells, but not DIVs. You can do some testing to confirm this.
Also, note that you cannot use the HEAD and BODY tags in an email. Those are generally stripped away.