Youtube - Get image default of video that you upload.

When you upload video to youtube. Youtube will generate some image of video. They help you show this image to your website.

This is format link of image.

You will have 4 images:
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

And some size of image:
http://img.youtube.com/vi/<insert-youtube-video-id-here>/default.jpg
http://img.youtube.com/vi/<insert-youtube-video-id-here>/hqdefault.jpg
http://img.youtube.com/vi/<insert-youtube-video-id-here>/mqdefault.jpg

Good luck to you