Approach to add my own overlay icons to pages in TYPO3

ext_localconf.php

<?php

if (!defined('TYPO3_MODE')) {
	die('Access denied.');
}

$boot = function($extensionKey) {
	// Hook for additional overlay icon
	$GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['t3lib/class.t3lib_iconworks.php']['overrideIconOverlay'][] =
		'EXT:' . $extensionKey . '/Classes/Hooks/OverrideIconOverlayHook.php:Sunzinet\SzPagesettings\Hooks\OverrideIconOverlayHook';
};

$boot($_EXTKEY);
unset($boot);

ext_tables.php

<?php

if (!defined('TYPO3_MODE')) {
	die('Access denied.');
}

$boot = function($extensionKey) {
	$GLOBALS['TBE_STYLES']['spriteIconApi']['spriteIconRecordOverlayPriorities'][] = 'content_from_pid_isset';
	$GLOBALS['TBE_STYLES']['spriteIconApi']['spriteIconRecordOverlayNames']['content_from_pid_isset'] = 'status-overlay-content-from-pid-isset';
	$GLOBALS['TBE_STYLES']['spriteIconApi']['coreSpriteImageNames'][] = 'status-overlay-content-from-pid-isset';
	$GLOBALS['TBE_STYLES']['spriteIconApi']['iconsAvailable'][] = 'status-overlay-content-from-pid-isset';

	$GLOBALS['TBE_STYLES']['inDocStyles_TBEstyle'] .= "
	.backgroundsize .t3-icon-overlay-content-from-pid-isset, .t3-icon-overlay-content-from-pid-isset {
		background: url('/typo3conf/ext/sz_pagesettings/Resources/Public/Icons/content_from_pid_isset.png') no-repeat 1px 4px !important;
	}";
};

$boot($_EXTKEY);
unset($boot);

OverrideIconOverlayHook.php

<?php
namespace Sunzinet\SzPagesettings\Hooks;

/**
 * Class OverrideIconOverlay
 *
 * @package Sunzinet\SzFalExpiredate\Hooks
 */
class OverrideIconOverlayHook {

	/**
	 * Override icon overlay
	 *
	 * @param string $table
	 * @param array $row
	 * @param array $status
	 * @return void
	 */
	public function overrideIconOverlay($table, $row, &$status) {
		if ($table == 'pages' && !empty($row)) {
			$this->overlayPages($row, $status);
		}
	}

	/**
	 * Sets overlay icon for pages with content_from_pid set
	 *
	 * @param array $row
	 * @param array $status
	 * @return void
	 */
	protected function overlayPages($row, &$status) {
		if (isset($row['content_from_pid']) && intval($row['content_from_pid']) > 0) {
			$status['content_from_pid_isset'] = TRUE;
		}
	}
}