How to change default image rename?

I think you can only access $file and do something like below.

add_filter('wp_handle_upload_prefilter', 'custom_upload_filter' );

function custom_upload_filter( $file ){
    $file['name'] = 'wordpress-is-awesome-' . $file['name'];
    return $file;
}

Also have a look how WP does it at wp-includes/file.php