How do we do that?
Simple! We need to set a blank space for text in SubMenuText property and use the style folder for submenu icons:
<tm:TextMenu runat="server" id="tm1"
specifies the text that is shown by the Menu Item when it has submenu
This is how the menu looks now:
If you want to use a different icon, simply create your own and change the url in style.css file
for classes with #tm_submenuCell
to point to your file: