2
Two ways:
1. Edit the main menu section of your theme's style.css to include an image (can be left, right or background), or
2. If you really do want a "custom menu" them look in the News section of this site for the latest release of the MultiMenu module.
To add an image to Main Menu then take a look at this code from the BlueHue theme as an example (applied to both Main Menu and User Menu - vary it to suit your needs):
td#mainmenu a {
display: block;
margin: 3px;
padding: 3px;
border-left: 4px solid #999;
border-bottom: 1px solid #999;
background: url(images/go.gif) no-repeat right;
}
td#mainmenu a:hover {
border-left: 4px solid #f90;
border-bottom: 1px solid #f90;
color: inherit;
background-color: #efefef;
}
td#mainmenu a.menuSub {
margin: 3px 3px 3px 12px;
}
td#usermenu a {
display: block;
margin: 3px;
padding: 3px;
border-left: 4px solid #999;
border-bottom: 1px solid #999;
background: url(images/go.gif) no-repeat right;
}
td#usermenu a:hover {
border-left: 4px solid #f90;
border-bottom: 1px solid #f90;
color: inherit;
background-color: #efefef;
}
td#usermenu a.highlight {
background: #f90;
}