Category Featured Image

I need help making default images for each of my categories. I tried your snippet of php code for the functions file, but it seemed to break the site. Here is the snippet I pasted at the end of my functions.php file:

function dfi_category( $dfi_id ) {
  if ( has_category( 'commodities' ) ) {
    return 157531; // the image id
  } else if ( has_category( 'dividends-income' ) ) {
    return 157533; // the image id
  } else if ( has_category( 'etfs' ) ) {
    return 157540; // the image id
  } else if ( has_category( 'forex' ) ) {
    return 157543; // the image id
  } else if ( has_category( 'investing' ) ) {
    return 157549; // the image id
  } else if ( has_category( 'market' ) ) {
    return 157553; // the image id
  } else if ( has_category( 'personal-finance' ) ) {
    return 157560; // the image id
  } else if ( has_category( 'real-estate' ) ) {
    return 157563; // the image id
  } else if ( has_category( 'retirement' ) ) {
    return 157571; // the image id
  } else if ( has_category( 'stocks' ) ) {
    return 157575; // the image id
  } else if ( has_category( 'trading' ) ) {
    return 157578; // the image id
  } else if ( has_category( 'us-world-news' ) ) {
    return 157730; // the image id
  }
  return $dfi_id; // the original featured image id
}
add_filter('dfi_thumbnail_id', 'dfi_category' );

Please help!

http://wordpress.org/plugins/default-featured-image/