Hi Herb
I found a hacking technique!
1. Open "Edit Draft" Landing page
2. Select "Property Sheet" and select a page body.
3. Add a element background "Value" to ;
background-image:url("http://<your path>/rtaImage.jpg")
Now, Background value is rgb(255,255,255);background-image:url("http://<your path>/rtaImage.jpg")

If you edit property sheet element again, sometimes that is trimed.
Please do your own risk.