You’re looking for the function is_page()
You could use the page id, the title or the slug in the function.
<?php if ( is_page('services') ) : ?>
<img...services
<?php elseif ( is_page('customer') ) : ?>
<img...customer
<?php else : ?>
<img..default
<?php endif; ?>
Another option is to use the post thumbnail feature from wordpress, then you can specify in the page which image you want on top (if you don’t already use them). ( http://codex.wordpress.org/Post_Thumbnails )