This will be so much easier once themes start enabling the new the_post_image function. In the meantime, try adding:
function my_post_image( $post, $thumb_width, $thumb_height ) {
$thumb_width = get_option('thumbnail_size_w');
$thumb_height = get_option('thumbnail_size_h');
$first_image = array();
$args = array(
'post_type' => 'attachment',
'post_mime_type' => 'image',
'numberposts' => 1,
'post_status' => null,
'orderby' => ID,
'post_parent' => $post->ID
);
$attachments = get_posts($args);
if ($attachments) {
foreach ($attachments as $attachment) {
$first_image = wp_get_attachment_image_src($attachment->ID, $size='thumbnail', $icon = false);
}
}
echo '<img src="' . $first_image[0] . '" width="' . $first_image[1] . '" height="' . $first_image[2] . '" alt="" />';
}
to your theme’s functions.php file. Then edit your archive template and try incorporating:
<?php
$thumb_width = get_option('thumbnail_size_w');
$thumb_height = get_option('thumbnail_size_h');
?>
<?php if (have_posts()) : while (have_posts()) : the_post(); ?>
[ usual post heading stuff ]
<?php my_post_image( $post, $thumb_width, $thumb_height );
the_excerpt();?>
[ usual post footer stuff ]
<?php else:?>
<?php endif;?>
