<script type="text/javascript">
tinyMCE.init({
    // General options
    mode : "textareas",
    theme : "advanced",
    plugins : "autolink,lists,spellchecker,pagebreak,style,layer,table,save,advhr,advimage,advlink,emotions,iespell,inlinepopups,insertdatetime,preview,media,searchreplace,print,contextmenu,paste,directionality,fullscreen,noneditable,visualchars,nonbreaking,xhtmlxtras,template,imagemanager,filemanager",
    
    // Theme options
    theme_advanced_buttons1 : "save,newdocument,|,bold,italic,underline,strikethrough,|,justifyleft,justifycenter,justifyright,justifyfull,|,styleselect,formatselect,fontselect,fontsizeselect",
    theme_advanced_toolbar_align : "left",
    theme_advanced_statusbar_location : "bottom",
    theme_advanced_resizing : true,
    width: "100%",
    height: "300",

    setup : function(ed) {
        ed.onEvent.add(function(ed, e) {
            console.debug('Editor event occured: ' + e.target.nodeName);
        });
        
        ed.onSetContent.add(function(ed, o) {
           console.debug('Set Content triggered');
        });
    }

});



</script>

<script>
jQuery(document).on('click', '.item img', function(event){
    addToPost();	
}); 

function addToPost() {
	var data = '<img src="http://www.shadedrelief.com/natural3/images/earth.jpg">';
	tinyMCE.activeEditor.selection.setContent(data);
}
</script>

<form method="post" action="dump.php">
    <textarea name="content"></textarea>
</form>

<ul class="gallery">
    <li class="item">
		<img src="http://www.shadedrelief.com/natural3/images/earth.jpg">
	</li>
</ul>