I was using JWPlayer 5, but right now moving to JWPlayer 6.
<script>
jwplayer('myElement2').setup({
file: 'intro.mp4',
image: 'intro.png',
skin: 'stormtrooper',
icons: 'false' // this doesn't work on JWPlayer 6
});
jwplayer('myElement2').getPlugin("display").hide();
</script>
On JWPlayer 5 it was icons: 'false'
and there were no play button.
The best way to do that would be to create your own skin, and leave that element out of the definition. But I think you can also do a little brute-force CSS:
Clicking the video frame will still start the playback.
If you are using Flash you need to make a custom skin to do this.
http://support.jwplayer.com/customer/portal/articles/1412123-building-jw-player-skins
If you are using HTML5, the answer above will suffice.