Overlay embedded slideshow

I've always been able to get objects to appear over the top a slide show (Wowslider specifically) by naming the object "overlay", putting it on a layer called "overlay", and then putting the following code in the head of the page:

<style type="text/css">
#overlay {
z-index: 11111;
}
</style>

This no longer works. How can we get objects to appear over embedded objects (or slide shows like Wowslider specifically) now?

I ended up getting this to work. It's that "one image for whole group" tik box on the "Image" tab. I made sure "PNG (best for graphics)" was selected too.