Francesco Francavilla is an artist of the people. The prolific illustrator shares a ton of art; concept, commissions, previews, his own fan art, whatever Mr. Francavilla is doing at the time on his tumblr page. In the month of May he created a work of art once-a-day and made it available for sale. Sgt. Rock, King Kong, Daredevil, Iron Man, Orion, Spider-Man were just some of the characters illustrated during the month.
The last entry for the month was this great illustration entitled "Bat Signal" featuring Batman and Commissioner Gordon. He includes some before pics as well as some insight on the tools he used. Francavilla is a must follow to see his incredible work.
Oh, and don't bother trying to purchase this one. It's sold out already.