Hello.
I finally figured how this menu template(menu.tpl) and other menu tpls are built and tied up
For example, I'm going to create new help menu.
Firstly, I made totally new menu template (named mymenu.tpl).
Code look something like this:
(I don't like using tables, so I used div tag instead. And ignore the class in div, I just put it to have my menu suited in my design)
I created graphic for menu title in jpg(named mm_help.jpg) for $menutitle and put it in images folder(in my case:{$ImagesDir}/myskin/").
Secondally, I create new help menu template(named myhelp.tpl).
I think you can delete this line "menu_title=$lng.lbl_help" because it's no longer used as menu title.
Finally, I put myhelp.tpl in home.tpl.
I don't know what's gonna happen when upgrade of x-cart comes.
But just for now, it works fine for me.