Advanced iFrame Pro - portrait video - thumbnail
This is inside the iframe. Unfortunately the iframe cannot really change this. What you can do is to use http://www.tinywebgallery.com/blog/advanced-iframe/advanced-iframe-pro-demo/lazy-loading#e25 -> 25 a - you can add your own preview image ove the iframe. Once you click on it and you enable autoplay you can decide by yourself which image is shown. And you also have lazy load. So no iframe is loaded at all until someone clicks it.
Best regards, Michael