Can I manually add a thumbnail web page to the Chrome homepage?

Yes, there is a way. Go to

%LOCALAPPDATA%\Google\Chrome\User Data\Default

You will find a file called "Preferences." Open the file with a text editor. You will see the list of 8 tabs at the bottom. Just modify the locations, i.e. the site that you want to appear.

As of 2/21/2012, Chrome version 17.0.963.56 m, most visited URL thumbnails are no longer stored in the Preferences text file, or any other easily editable text file.

It's probably stored in an SQLite database. Here's more info on the this frustrating "enhancement" to newer versions of Chrome:

• Editing 'Most Visited' items URL via Database

It was bad enough they made it so inconvenient to pick your own favorite sites to begin with, now they don't let you at all. (I have a feeling it's because they are trying to push Apps.)

I solved the problem by dragging the URL shortcuts I really needed to my Start Menu.

I'll probably stop using the "New Tab page" from now on.

Looks like an extension called Speed Dial is the answer.