The following parameters when added to the body tag will fix the background image of the html document. That means, when you scroll down the page, the background will remain in its place and will not change or scroll.
<body background="images/background.jpg" bgproperties=fixed>
If you want to delete a file or an image from the server via an interface from you website, you can use the following code
$filearray = explode("/", $filename);
$filecountno = count($filearray);
$filecountno = $filecountno-1;
$myfilename = $filearray[$i];