Is there a better, more jQuery-ish way of handling this image substitution?
var image = $(obj).children(\"img\");
if ($(image).attr(\"src\") == \"Images/TreeColl
Your image object would already be a jQUery instance so there is no need for you to pass it through $(...) again.
A good practice is to prepend variables that are jquery instances with $ and use them directly thereafter.
var $image = $(obj).children("img");
if ($image.attr("src") == "Images/TreeCollapse.gif")
$image.attr("src", "Images/TreeExpand.gif");
else
$image.attr("src", "Images/TreeCollapse.gif");