After Benedict Cumberbatch was announced as the actor behind Smaug in The Hobbit, it was only a matter of time before people started creating art combining his two most famous characters. io9 has a great collection of such creations, including this piece by DeviantArt user Ocean-Crystal.
@Jill. You missed the best part. Not only is Benedict Cumberbatch Smaug/Sherlock, Martin Freeman, who plays Bilbo, played Watson in the same series.