Bulk import images using node images

This is how I solved it. Be aware, I don't really know what I am doing yet in terms of Drupal development so use at your own risk.

// The problem: A lot of images in named folders. The folders has the same name
// as the nodes they are to be "attached to" with node_images.
// I have also customised the node_images module but have tried to edit out 
// anything related to those customisations in this script but if it doesn't
// work for you, be aware. For example I have made node_images to save images
// in a subfolder with the node id. 

// Ideas on how to write one off scripts for drupal came from
// http://drupal.org/node/67887 
// so cred to Victor Kane - victorkane at awebfactory dot com dot ar
// and Jeff Vogelsang - jeffvogelsang at pqa dot com
// I'm at petterw at kenandi dot com

// CONFIGURATION
// Change the value below to TRUE when you want to run the script After running,
// immediately change back to FALSE in order to prevent accidentally executing
// this script twice.
// NOTE: I find the best way to do this is to leave it false. When you are ready
// to execute, set to this variable to true, and then click Preview. The script
// will execute, but will not be saved with the value set to true. This prevents
// accidentally saving the script with the value set to true. Also, it prevents
// the unfortunate situation where the cron job runs while it's set to true,
// and you get double imports.
$active = false;
// Set the folder with the images to import. I used a drupal subfolder, seemed easier so 
$import_folder = 'sites/all/files/import/a';
// Importing a lot of images can take a while, especially if they are big and needs to 
// be scalled, so set the PHP script time limit, how long the script can run before it is
// terminated.
set_time_limit (120);

// Bootstrap Drupal
include_once "includes/bootstrap.inc";
include_once("includes/common.inc");
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

// Check for the script being enabled.
if ($active) {
       import_images($import_folder);
} else {
       print "Variable active is set to false.";
}

function import_images($import_folder) {
  // Get all the files and folders of the import folder
  $folders = scandir($import_folder);
  // Iterate through all the files and folders  
  foreach($folders as $folder){    
    $folder_path = $import_folder . '/' . $folder;
    // Make sure it is a directory and not a file
    if (is_dir($folder_path) && $folder != "." && $folder != "..") {
      // Check if there is a node named the same as the directory
      if($node = node_load(array(title => $folder))){
        // Start inserting all images of that folder
        insert_images($import_folder,$folder, $node);
      }
    }
  }
}
    
function insert_images ($import_folder, $folder, $node) {
    $output = '<ul>';
    $folder_path = $import_folder . '/' . $folder;

    if ($handle = opendir($folder_path)) {
        // Set the destination directory
        $dest = _node_images_get_directory($node);

        // Create the destination folders
        $directories = explode("/", $dest);
        $dirs = array();
        foreach($directories as $directory) {
          $dirs[] = $directory;
          if (!file_check_directory(implode("/", $dirs), 1)) {
            mkdir(implode("/", $dirs));
          }
        }

        $i = 0;
        // Go through each file in that folder
        // Parts taken from the node_images upload function
        while (false !== ($infile = readdir($handle))) { 
            if ($infile != "." && $infile != "..") { 
                $i++;
                $file = new stdClass();
                $file->filename = $infile;
            
                // Create temporary name/path for newly uploaded files.
                $file->filepath = $folder_path . '/' . $file->filename;
            
                // Scale image
                $file = _upload_image($file);
                
                // Validation from upload.module
                $user = 1;
                $fid = 'upload_'.$user;
                $node->files = array($fid => $file);
                _upload_validate($node);
                if (!isset($node->files[$fid])) return FALSE;
             
                // Move the file so if it the file is no longer in the import folder you can
                // assume it worked. Otherwise just use the drupal file_copy function 
                if (file_move($file, $dest)) {
//                if (file_copy($file, $dest)) {
                  $thumb = _node_images_create_thumbnail($file->filepath);
                  $file->filesize = filesize($file->filepath);
                  db_query("INSERT INTO {node_images} (nid, uid, filename, filepath, filemime, filesize, thumbpath, thumbsize, weight, description, page, position)
                           VALUES (%d, %d, '%s', '%s', '%s', %d, '%s', %d, %d, '%s', %d, %d)",
                  $node->nid, 1, $file->filename, $file->filepath, $file->filemime, $file->filesize,
                  $thumb->filepath, $thumb->filesize, 0, '', 0,0);
                }
            } 
        }
        $output .= '<li>' . $i . ' images for: ' . $folder . ' into nid: ' . $node->nid;
        closedir($handle);
    }
  $output .= '</ul>';
  print $output;
}

Just create a new page and put this in the body with input type set to php.