Hi,
It has been reported that iPad/Safari doesn't show preview image. Preview image is working on all desktop browsers.
Although, in IE9, when loading the page first time it doesn't show preview image but refreshing the page shows preview image.
All the information is in thread at http://www.longtailvideo.com/support/forums/jw-player/setup-issues-and-embedding/24541/jwplay-previe...
Thanks
@Jaswinder -
We have some bug fixes in place which address the preview image in HTML5 on iOS. Please download the latest preview build here and let us know if that works for you:
http://developer.longtailvideo.com/trac/browser/trunk/fl5/