SuperTester,
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
</style>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
<script>
$(function(){
$(".single-room").each(function(indx, el){
$(".count",el).text($('img',el).length)
});
});
</script>
</head>
<body>
<div class="single-room">
<img src="">
<img src="">
<span class="count"></span>
</div>
<div class="single-room">
<img src="">
<img src="">
<img src="">
<span class="count"></span>
</div>
</body>
</html>