Use background images without knowing programming? I'm trying to set up a site using Drupal 7, and have very little knowledge of the stuff under the hood.  If the answer is to edit some css, please give VERY simple instructions.

Is there a simple way to put background images in the Acquia Marina theme?

Or, are there similar looking themes that have this facility built in?

Thanks!
You should change the body background selector in the css file of the template, for example

body{ background: url("path to image");}


More info how to use background css