Yakir,
Most of the articles on the HP have no preview displayed even though an image is placed in the admin panel. Just have a look at all the titles on Wall.co.il and see.
Also, see a category page for example http://www.wall.co.il/category/%D7%9E%D7%A2%D7%A0%D7%99%D7%99%D7%9F/
Thanks