gistfile1.php

<?php

// Add to your theme's functions.php
add_filter( 'searchwp_indexed_post_types', 'my_searchwp_indexed_post_types' );
add_filter( 'searchwp_engine_settings_default', 'my_searchwp_engine_settings_default', 10, 2 );

function my_searchwp_indexed_post_types( $post_types ) {
    if ( ! in_array( 'attachment', $post_types ) ) {
        $post_types[] = 'attachment';
    }
    return $post_types;
}

function my_searchwp_engine_settings_default( $settings, $query ) {
    $settings['attachment']['enabled'] = true;
    $settings['attachment']['weights']['title'] = 20;
    return $settings;
}