Video Instructable Thumbnails Answered

I recently started making video Instructables via YouTube. I've found it to be an excellent method of getting my how-to projects two different places at one time. However, I have noticed one issue. This site requires you to use a separate thumbnail. I don't take a picture every time I make a video, (sometimes I really can't) so I end up having to copy some online picture instead. Why can't we use our YouTube thumbnails for videos? I'd really appreciate it if this could become a possibility.