pstagg

Some may be interested in this variant:

For image links I wanted something functional equivalent to:
previous_post_link('<li>%link</li>');

So thanks to this thread I came up with this:

In functions.php:

function ps_previous_image_link( $f ) {
    $i = ps_adjacent_image_link( true );
	if ( $i ) {
		echo str_replace("%link", $i, $f);
	}
}

function ps_next_image_link( $f ) {
    $i = ps_adjacent_image_link( false );
	if ( $i ) {
		echo str_replace("%link", $i, $f);
	}
}

function ps_adjacent_image_link($prev = true) {
    global $post;
    $post = get_post($post);
    $attachments = array_values(get_children(Array('post_parent' => $post->post_parent,
	      'post_type' => 'attachment',
	      'post_mime_type' => 'image',
	      'orderby' => 'menu_order ASC, ID ASC')));

    foreach ( $attachments as $k => $attachment ) {
        if ( $attachment->ID == $post->ID ) {
            break;
		}
	}

    $k = $prev ? $k - 1 : $k + 1;

    if ( isset($attachments[$k]) ) {
        return wp_get_attachment_link($attachments[$k]->ID, 'thumbnail', true);
	}
	else {
		return false;
	}
}

In image.php:

<ol>
<?php ps_previous_image_link( '<li>%link</li>' ) ?>
<?php ps_next_image_link( '<li>%link</li>' ) ?>
</ol>

Thanks guys.