exit404 function impacts website cohesion

For dynamic images management, your exit404 function is great for debugging, but maybe you should modify your function to:

function exit404( $message ) {
	global $wp_query;
	$wp_query->set_404();
	status_header(404);
}

This way, you’ll redirect to the site global 404 management system and page.
As a webmaster, I think it’s way better for the website and the brand image than a one line “debug” error…
Or maybe could you propose a debug mode to switch between both behaviors?
Not meaning to be rude at all, just wanting to participate improving your great plugin by sharing my needs and ideas.