Get Youtube Video Thumb Picture

var playListURL = 'http://gdata.youtube.com/feeds/api/playlists/B2A4E1367126848D?v=2&alt=json&callback=?';
var videoURL= 'http://www.youtube.com/watch?v=';
$.getJSON(playListURL, function(data) {
    var list_data="";
    $.each(data.feed.entry, function(i, item) {
        var feedTitle = item.title.$t;
        var feedURL = item.link[1].href;
        var fragments = feedURL.split("/");
        var videoID = fragments[fragments.length - 2];
        var url = videoURL + videoID;
        var thumb = "http://img.youtube.com/vi/"+ videoID +"/default.jpg";
        list_data += '<li><a href="'+ url +'" title="'+ feedTitle +'"><img alt="'+ feedTitle+'" src="'+ thumb +'"</a></li>';
    });
    $(list_data).appendTo(".cont");
});

This will out put a list of a thumbs of a video playlist of youtube

Demo: Fiddle for the playlist you have provided

http://img.youtube.com/vi/{video-id}/default.jpg 
http://img.youtube.com/vi/<insert-youtube-video-id-here>/0.jpg
http://img.youtube.com/vi/<insert-youtube-video-id-here>/1.jpg
http://img.youtube.com/vi/<insert-youtube-video-id-here>/2.jpg
http://img.youtube.com/vi/<insert-youtube-video-id-here>/3.jpg

Since adding the video ID and get the thumbs of the videos from youtube