You know, if you put this then you will be able to show the video with the thumbnail.
1.Click the Special BBCode icon, which is the third on the first row.
2.When you open Special BBCode a page will pop up.
3.On the page scroll down, once you see youtube, click it.
4.On youtube paste the link of the video.
5.Once you do that click OK.
6.Then click save changes.
Now you have a youtube video with a thumbnail.