Detect tag page and include an Image for that specific tag

Here are 2 solutions:

Using Tag titles

<?php
switch( single_tag_title( '', false ) ) {
    case 'Books' :
        include 'tags/books.php';
        break;
    case 'Tables' :
        include 'tags/tables.php';
        break;
    default :
        break;
}
?>

Using tag slugs:

<?php
if ( is_tag( 'books' ) ) {
    include 'tags/books.php';
}
else if ( is_tag( 'tables' ) ) {
    include 'tags/tables.php';
}
?>