I created a Parent Theme following a bunch of ideas from several WordPress fans. In my host (goDaddy.com), which is configured for multisites, I created two child sites at "dumplings" and "AccesoriosCelularPR".
As far as CSS for the "header" is concerned, both child sites' are identical, except for the background image's NAME, as follows:
Code for "style.css":
background-color: none !important;
background-image: url(images/<image name>.png);
Code for "backgrounds_CSS_only.css":
I know you guys are busy but any guidance will be appreciated. Thanks!!!