This topic was started by soaringeagle, but I've found a way to change the set up, so that the Youtube thumbnail will not show on new uploaded Youtube videos.
This is what you do. Go to a previously posted Youtube video on your site. Go to " Get Embed code and copy the HTML code. Paste the code in Word or NotePad. On the pasted code you will see a set of numbers followed by letters (e.g http://www.youtube.com/embed/1y6smkh6c-0?). Now go to the new Youtube video you want to post and copy the number and letter code and replace it on the code you pasted on Word or Notepad. Replace all number and letter code before the question mark. Copy the entire new code and and paste on your site. You should now be able to see the video without the Youtube thumbnail. Let me know how it goes.