The David Tennant Treat 4 Today today is a photo.
It's actually the first photo which pops up on a Google search for David Tennant images and comes from a Wordpress Blog.
The photo itself was taken as David Tennant attended the premiere of Harry Potter and The Order Of The Phoenix on 3rd July 2007 in Leicester Square, London. (David had appeared in the earlier Harry Potter movie The Goblet Of Fire.)
There are loads of photos of David from this premiere and this is one of the best. It also features an appearance by his famous velvet suit!