This restartless add-on provides a different New Tab page for Mozilla Firefox
New-Tabmarks is a Firefox extension that replaces the default New Tab page with a cleaner one, which displays recently closed tabs, frequently visited sites, the bookmarks toolbar, and shortcuts for the most popular search engines (e.g. Google, Bing, Yahoo).
New-Tabmarks is an open source add-on designed to work with Mozilla Firefox 16.0 and later. It is accessible through the about:newtab shortcut.
This add-on doesn't require you to restart the web browser.