Get featured image outside the loop using foreach

First you will need to get a list of all available sizes on your site. This function get_intermediate_image_sizes() will do that. You can then pass the results of that to image_get_intermediate_size() along with the post id and

<?php $sizes = get_intermediate_image_sizes(); ?>
<?php foreach($major_data as $postID) { ;?>
    <?php $postData = get_post( $postID );?>
    <?php print $postData->post_title;?><br>
    <?php var_dump(image_get_intermediate_size( $postID, $sizes )); ?> 
<?php } ?>

more info on this function get_intermediate_image_sizes()

lot of good functions for dealing with images in the media.php wordpress core file