Image is sibling thus closest()
will not work. You can use next()
Use
$(document).ready(function() {
$('.stn_uploader .delete').click(function() {
$(this).next('img').remove();
});
});
OR
$(document).ready(function() {
$('.stn_uploader .delete').click(function() {
$(this).closest('.stn_uploader').find('img').remove();
});
});