poster parameter for the video shortcode

Syntax

[video
src,mp4,m4v,webm,ogv,wmv,flv="| URL - If omitted uses first attachment"
poster="| URL - Placeholder image"
loop="off| on - Allow looping of media"
autoplay="off| on - Causes media to autoplay"
preload="none| auto| metadata - How the audio should be loaded"
height="| numeric - Required height"
width="| numeric - Required width"]