Overlay an image over the slideshow or image slide

Hi,

I don't have success trying overlay an image over the slideshow or just to a single slide image.

My code (description field) to try overlay image.jpg

<h1>Some text</h1>
<img src="http://domain.tld/image.jpg" />
<h1>Some text</h1>

Just displays the text.
It was supposed to work this way?

thanks