Dear Webkrea
Open your site / templates/ja_beryl/css/template.css around line 652 see this code :
#ja-container-f {
background: url(../images/cw-bg.gif) repeat-x left top;
clear: both;
padding: 0;
}
You can remove or edit the reference to the image here.
Well, a quick way to hide it on main page but to show on others is. Clone your template and assign the clone (with the edited code) assigned to main page and your original template assigned to all the other pages.
Though i have never done that, saw a guy who did this.
For cloning, you will need to change the template folder name and template name in the xml file.
Regards
Arvind