It’s so simple to embed a YouTube video, with thumbnail into your site. Ditch any clever PHP scripts or completed jQuery libraries.
So you have a Youtube video – http://www.youtube.com/watch?v=t4_dZPVg8KI
Take the video ID t4_dZPVg8KI and craft yourself a link to YouTube’s image server;
http://img.youtube.com/vi/t4_dZPVg8KI/1.jpg
You have a choice of 1.jpg or 2.jpg or 3.jpg
How easy is that!