The coverImage feature does not support changing the image dynamically. However you could use the canvas for images. See the example below. With this you can change the image dynamically with code like this, you can try this in your browser's developer console:
$f().getPlugin("canvas").css({ background: 'url(/img/demos/thumb2.jpg) no-repeat 50pct 50pct' })
HTML setup for the player
<!-- include latest Flowplayer javascript file -->
<script language="javascript" src="path/to/flowplayer-3.2.8.js"></script>
<!-- player container with optional splash image -->
<a href="path/to/video_file" id="playerContainer">
<img src="path/to/splash_image" />
</a>
JavaScript coding
Following script will install Flowplayer into our player container
<script language="javascript">
// our custom configuration is given in third argument
flowplayer("playerContainer", "path/tohttp://releases.flowplayer.org/swf/flowplayer-3.2.11.swf",{
clip: {
url: 'http://releases.flowplayer.org/data/fake_empire.mp3'
},
canvas: {
// a canvas image centered 50% vertically and horizontally
background: 'url(/img/demos/thumb1.jpg) no-repeat 50pct 50pct'
}
});
</script>