Rotating banners in Sub Pages Only

I have a customer who wants to do a directory website. He is planning to sell one page websites to small businesses. He wants three rotating banners for each of their sites. There may end up being several hundred if he is successful.

Using Juggledad's code:

body.page-id-2 div#imagecontainer {
background-image: url('http://yourdomain.com/wordpress/wp-content/hdr_images/page_2.jpg') !important;
}

I can see having a special header for one page. Will it work for more than one image? i.s.
body.page-id-2 div#imagecontainer {
background-image: url('http://yourdomain.com/wordpress/wp-content/hdr_images/page_2.jpg, http://yourdomain.com/wordpress/wp-c...es/page_2a.jpg, http://yourdomain.com/wordpress/wp-c...es/page_2b.jpg') !important;
}

I can see the HTML/CSS file becoming enormous!