There are, or at least WERE additional Menu PSD's available, though not from Adobe. There was a UK company, that had a rather large portfolio of Menu PSD's for purchase, though, IIRC, most were of a wedding theme.
Also, Jon Geddes' PreComposed has many active AE Menus for purchase, as well.
Many users just sort through the Library Menus (and Buttons), to find a structure, that works in their Project, and then use Photoshop (though Encore can modify Menus too) to customize that structure, to suit their needs. Over the years, I have customized many of the Library Templates, and Saved many, for later use in similar Projects. If one understands the building blocks of the Menu PSD's, Photoshop makes that operation very easy.
I also find it useful to study the construction of other Library Templates, for graphic design ideas, and will often press those ideas into use, on other Library Templates, with a structure, that works for me. I also rely on several DVD Menu graphic design books, for ideas. Most do not go into great detail on the mechanics of the construction, but more on the graphic design of the Menus - still, they get me thinking. Many commercial DVD's are great resources for ideas of what you think works well, both graphically and mechanically.
Good luck,
Hunt