Well, in the spec it's currently not a tag, but an attribute... and it does work like the current sites that will load a picture before playback.
Originally Posted by Karpie
Technically thinking on it I believe it should be a separate element -- as an ATTRIBUTE of the video tag. I'm ok with it as an attribute (though it should be on object instead of adding some new trash tag)... This way you could have the poster embedded on the VIDEO tag, with a separate IMG for people for whom the video tag fails.
Would be how the current version of the specification would work -- which is why I don't see the need for a new tag as there's MORE than enough drop-through present.
alt="Describe the movie for non-visual users here"
Your system is unable to play this movie