You can remove it this way:
function removeLabel() {
document.getElementById('picturediv').removeChild(document.getElementById('picturediv').getElementsByTagName('label')[document.getElementById('picturediv').getElementsByTagName('label').length - 1]);
}
edit:
The function with comments:
function removeLabel() {
var parentNode = document.getElementById('picturediv'); // The parentNode of the label element
var tagsWithLabel = parentNode.getElementsByTagName('label'); // All elements with tag name label
var length = tagsWithLabel.length; // The length of the node array
parentNode.removeChild(tagsWithLabel[length - 1]); // Deleting the last element with tage name label from parentNode.
}
edit because of comment:
function removeLabel(id) {
document.getElementById(id).removeChild(document.getElementById(id).getElementsByTagName('label')[document.getElementById(id).getElementsByTagName('label').length - 1]);
}
to delete label 1: removeLabel('picturediv');
to delete label 2: removeLabel('picturediv2');