custom field images do not display until page save

Question

Pragmatically i am adding custom field images to my page. The process is

1. I create the post
2. I update to apply a template
3. I add my custom fields which includes an image

This is working and i see the image in wordpress admin. However the following doesn't work in my template until i save the post in the editor.

    <img src="<?php echo $largeImage['url'] ?>" />

I thought perhaps i need to add a 4th step which is save the post again.

 update_post_meta($post_id);

Which doesn't work. What am i missing here. Do i have to clear the cache or something?

EDIT

1) I create the post

   $post_id = wp_insert_post(
                array(
                    'post_name' => $slug,
                    'post_title' => $title,
                    'post_content' => $content,
                    'post_type' => $post_type,
                    'post_author' => $author_id,
                    'comment_status' => 'closed',
                    'ping_status' => 'closed',
                    'post_status' => 'publish',
                )
            );

2) I apply template

update_post_meta($post_id, '_wp_page_template', $template_rel_path);

3) I save custom fields

    public function update_artwork_post_meta($post_id)
    {
        $meta_values_to_set = array (
            'img_url' => $this->raw['img_url'],
            'artist' => $this->raw['artist'],
            'artwork_html' => $this->raw['artwork_html'],
            'dimensions' => $this->raw['dimensions'],
            'period_id' => $this->raw['period_id'],
            'full_title' => $this->raw['full_title'],
            'artist_sort' => $this->raw['artist_sort'],
            'artist_id' => $this->raw['artist_id'],
            'title' => $this->raw['title'],
            'status' => $this->raw['status'],
            'description' => $this->raw['description'],
            'medium' => $this->raw['medium'],
            'id' => $this->raw['id'],
            'modification_date' => $this->raw['modification_date'],
            'provenance' => $this->raw['provenance'],
            'artist_sort_title_year' =>         $this->raw['artist_sort_title_year'],
            'preview_image' => '',
            'portrait' => '',
            'landscape' => '',
            'width' => '',
            'height' => ''
        );

        foreach($meta_values_to_set as $key => $meta_value){ 
            if ($key == "img_url"){
                 $tempimgurl = $meta_value;
                 $meta_value = somatic_attach_external_image( $url = $meta_value, $post_id = $post_id);
            }

            $success = $this->update_meta($post_id, $key, $meta_value );
        }
    }


    function somatic_attach_external_image( $url = null, $post_id = null, $thumb = null, $filename = null, $post_data = array() ) {
    if ( !$url || !$post_id ) return new WP_Error('missing', "Need a valid URL and post ID...");
    require_once( ABSPATH . 'wp-admin/includes/file.php' );
    // Download file to temp location, returns full server path to temp file, ex; /home/user/public_html/mysite/wp-content/26192277_640.tmp
    $tmp = download_url( $url );

    // If error storing temporarily, unlink
    if ( is_wp_error( $tmp ) ) {
        @unlink($file_array['tmp_name']);   // clean up
        $file_array['tmp_name'] = '';
        return $tmp; // output wp_error
    }

    preg_match('/[^\?]+\.(jpg|JPG|jpe|JPE|jpeg|JPEG|gif|GIF|png|PNG)/', $url, $matches);    // fix file filename for query strings
    $url_filename = basename($matches[0]);                                                  // extract filename from url for title
    $url_type = wp_check_filetype($url_filename);                                           // determine file type (ext and mime/type)

    // override filename if given, reconstruct server path
    if ( !empty( $filename ) ) {
        $filename = sanitize_file_name($filename);
        $tmppath = pathinfo( $tmp );                                                        // extract path parts
        $new = $tmppath['dirname'] . "/". $filename . "." . $tmppath['extension'];          // build new path
        rename($tmp, $new);                                                                 // renames temp file on server
        $tmp = $new;                                                                        // push new filename (in path) to be used in file array later
    }

    // assemble file data (should be built like $_FILES since wp_handle_sideload() will be using)
    $file_array['tmp_name'] = $tmp;                                                         // full server path to temp file

    if ( !empty( $filename ) ) {
        $file_array['name'] = $filename . "." . $url_type['ext'];                           // user given filename for title, add original URL extension
    } else {
        $file_array['name'] = $url_filename;                                                // just use original URL filename
    }

    // set additional wp_posts columns
    if ( empty( $post_data['post_title'] ) ) {
        $post_data['post_title'] = basename($url_filename, "." . $url_type['ext']);         // just use the original filename (no extension)
    }

    // make sure gets tied to parent
    if ( empty( $post_data['post_parent'] ) ) {
        $post_data['post_parent'] = $post_id;
    }

    // required libraries for media_handle_sideload
    require_once(ABSPATH . 'wp-admin/includes/file.php');
    require_once(ABSPATH . 'wp-admin/includes/media.php');
    require_once(ABSPATH . 'wp-admin/includes/image.php');

    // do the validation and storage stuff
    $att_id = media_handle_sideload( $file_array, $post_id, null, $post_data );             // $post_data can override the items saved to wp_posts table, like post_mime_type, guid, post_parent, post_title, post_content, post_status

    // If error storing permanently, unlink
    if ( is_wp_error($att_id) ) {
        @unlink($file_array['tmp_name']);   // clean up
        return $att_id; // output wp_error
    }

    // set as post thumbnail if desired
    if ($thumb) {
        set_post_thumbnail($post_id, $att_id);
    }

    return $att_id;
 }

I call this with the following hook

add_action('init', 'process_artwork');

function process_artwork(){
    if(isset($_GET['ss-process'])) {
     // process $_POST data here

            if ( current_user_can( 'manage_options' ) ) {
               // business logic that calls wp_insert_post

            }
    }
}