Hi Pappy
The background uses the 'background-size:cover' property which can act differently to what you may expect on some mobile devices. You could try adding the following to the Custom CSS field of your templates parameters which will disbale this property on mobile devices..
@media only screen and (max-width: 1024px) {
#body_bg, #container_header {
-webkit-background-size: auto !important;
-moz-background-size: auto !important;
-o-background-size: auto !important;
background-size: auto !important;
}}
Ciarán