title: YouTube embedded video: set different thumbnail
body: <p>I want to embed a video from YouTube that is not mine (so I can not change it at YouTube). The video has a thumbnail that is not representative for the video (I refer to the initial still that is shown when you embed a video, shown before the user plays it). </p>
  
  <p>Is there a way to set the time of the still, for instance I tried passing <code>?s=XXX</code> but this does not work.  Or another way that comes natively with YouTube? </p>