Sample code
<obout:ImageZoom ID ="ImageZoom1" ImageUrl="~/ImageZoom/images" ShowFooter="false" BackgroundOpacity="100" ThumbnailHeight="250" ThumbnailWidth="250" ></obout:ImageZoom>
C#
ImageZoom1.ShowFooter="false";
ImageZoom1.BackgroundOpacity="100";

Add the following css class to set the backgroung colour.
<style type="text/css">
.oizZoomModeBg
{
background-color:Black !important;    
z-index:50 !important;
position:fixed !important;
}
</style>