The code you gave there would cause problems when going to https
call the images like this instead {$ImagesDir}/image.jpg
Code:
<TABLE border=0 cellPadding=5 cellSpacing=0 width="100%">
<TR>
{if $link_href}
<TD class=VertMenuTitle background="{$ImagesDir}/tabs.gif" height=26 valign=center width=80%>
<font class=VertMenuTitle>{$menu_title}</font></TD>
{else}
<TD class=VertMenuTitle background="{$ImagesDir}/tabs.gif" height=26 valign=center width=80%><font class=VertMenuBoxNewsTitle>{$menu_title}</font></TD>
{/if}
</TR>
<TR>
<TD colspan="2" class=VertMenuBox>{$menu_content}
</TD></TR>
</TABLE>