Артем

$('#main').append('<div class="block"> <img src='+newImg+' alt="" width="100%" height="100%"> </div>');

url: 'mailer/send_letter.php?param1=value1&param2=value2',

$('input[type=checkbox]').each(function () {
           if (this.checked) {
               console.log($(this).val()); 
           }
});