Add the data-pin-nopin attribute to popup optin images to exclude them from Pinterest share options. https://developers.pinterest.com/docs/widgets/pin-it/#nopin
jQuery(document).ready(function($) {
$(document).on('OptinMonsterLoaded', function(event, data, object){
$('#om-' + data.optin + ' img').attr('data-pin-nopin', 'true');
});
});