Place the embedded video in a div that is invisible:
<div id="video" style="display: none;"> embedded video code here </div>
Then give the img
an id too:
<img id="videopic" src="videopic.jpg" alt="Video Picture" />
Then, put a link round the image pointing to some JavaScript which hides the image and shows the embedded video:
<a href="javascript:document.getElementById('video').style.display = 'block'; document.getElementById('videopic').style.display = 'none'; void(0);">
<img id="videopic" src="videopic.jpg" alt="Video Picture" />
</a>
So, the full code would be:
<div id="video" style="display: none;"> embedded video code here </div>
<a href="javascript:document.getElementById('video').style.display = 'block'; document.getElementById('videopic').style.display = 'none'; void(0);">
<img id="videopic" src="videopic.jpg" alt="Video Picture" />
</a>