This was already in the v10 branch, so I have uploaded the small change for you. I thought I'd actually done this for you, but perhaps it was for adding newsletter thumbnails to something else and I'd prepared changes for other content types also.

Thanks Chris!

When I first come to the 'Send out/schedule issue: New content' screen, now I get multiple alerts for youtube URL, like--

"The website software cannot access the file from the given URL (http://img.youtube.com/vi/YQ9_-DtLaNU/0.jpg). If this file was just uploaded, then there may be an issue with a .htaccess file or the temporary directory file permissions."

If I go through the process do a preview of the newsletter, I do see the thumbnails, however they are aligned to the right of the window instead of on the left under the video title, not sure if you intended that.

Yes, I noticed these errors. Those videos have been removed from Youtube. One down-side of remote hosting I'm afraid :(.

The thumbnails were supposed to be right-aligned, which hasn't changed. I did notice they weren't consistently aligned though due to a flaw in the template change I posted on the forum; I just corrected that. It makes it easier to find the missing video as you can now clearly see where the broken thumbnail is.