If you add this to functions.php, this will update the options as set.
function custom_image_size() {
// Set default values for the upload media box
update_option('image_default_align', 'center' );
update_option('image_default_size', 'large' );
}
add_action('after_setup_theme', 'custom_image_size');
You can update the options as you need.