It's simple to do with this addon
https://fulltextsearch.org/wpfts-addon-files-only-1.0.1.zip

It contains some code to limit post_type to 'attachment' only:

add_action('pre_get_posts', function(&$wpq)
{
	if ($wpq->is_search && $wpq->is_main_query()) {
		$wpq->set('post_type', array('attachment'));
		$wpq->set('post_status', array('inherit'));
	}
});

Pretty simple. If you want to set up your own post_types, just modify this code. You can read about full WP_Query() parameters at the Wordpress official documentation.

Yes, of course, all the same values that you're usually using for WP_Query() will work!

You can specify parameters in case you want to call WP_Query() manually or you can use the pre_get_posts hook in case you want to intercept the main query.

What do you actually plan to do?