For static images, such as those used with template files, use CSS. For dynamic images, such as those that change from page to page, use HTML.
If you really want to create a CSS file for each page, which is rather stupid, you can do it pretty easily with PHP. Just make a folder called CSS. Then for each page, make a CSS file. Like, home.css, contact.css...etc. Then dynamically call the CSS file with PHP depending on the page. For simplicities sake, I'll just show you a snippet of code that uses GET for the page.
PHP Code:
<?php
$page = $_GET['page'];
echo '<link rel="stylesheet" type="text/css" href="css/'.$page.'.css" />';
?>