For the rounded corners on the end, this is not part of the menu, rather part of the styleing for the div is contained in.
you would need to create three divs:
<div class="menuCenter>CSS Menu Writer menu Goes here</div>
the menuLeft div will get the left rounded corner image as the background, the menuRight div will get the right rounded corner image as the background.
To have differant sizes for the main navigation items, you will need to add an inline style to the menu items after the menu is created, for example:
<li><a href="#" style="width:40px;">home</a></li>