Tooltips already exist on the interface elements of new tab page, including (on thumbnails) pin and remove, and (on the page itself) restore and hide New Tab page.
On the thumbnails themselves, the tooltip should give the full string title of the site.
Created attachment 587548 [details]
Mockup: Tooltip added. Not that you really needed one
*** Bug 717109 has been marked as a duplicate of this bug. ***
Created attachment 587665 [details] [diff] [review]
Simple patch, adding tooltips.
*** Bug 721442 has been marked as a duplicate of this bug. ***
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:12.0a2) Gecko/20120220 Firefox/12.0a2
Mozilla/5.0 (X11; Linux x86_64; rv:12.0a2) Gecko/20120221 Firefox/12.0a2
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0a2) Gecko/20120220 Firefox/12.0a2
Verified on Firefox 12. Tooltips are no available for page titles.