You must have to put your images in media folder and est full path. Please check the below code i changed.

	<?php
	require_once 'app/Mage.php';
	Mage::app();
	Mage::app()->getStore()->setId(Mage_Core_Model_App::ADMIN_STORE_ID);
	$importDir = Mage::getBaseDir('media') . DS . 'bulkimages/101/';
	
	$productsData = array('Purple-Crown-Ring-MFAS.jpg','Purple-Crown-Ring-MFC.jpg','Purple-Crown-Ring-MSAS.jpg','Purple-Crown-Ring-MSF.jpg');

    $productSKU = '111';
	$ourProduct = Mage::getModel('catalog/product')->loadByAttribute('sku',$productSKU);

	foreach($productsData as $fileName){
		$filePath = $importDir.$fileName;
		if (file_exists($filePath)) {
			$ourProduct->addImageToMediaGallery($filePath, array('image', 'small_image', 'thumbnail'), false, false);
			$ourProduct->save();
			echo "done ";
		} else {
			echo $productSKU . " not done";
			echo "<br>";
		}   
	}
	?>