I was perusing DeviantArt and came across some interesting airship art. One artist in particular, The-Necromancer, has an entire gallery (7 pages worth) of airship art. Some I like, some I don't. Some are realistic, some artsy, and some I do not like. Despite the Communist iconography of the artist's avatar and a few of his other galleries, I found some of the airship art quite compelling. Its worth taking a look if you're into airships.
Another artist, JanBoruta, has a Steampunk gallery with number of pencil sketches of airships, aircraft, steam-powered armored vehicles, etc.
A third, donaguirre, has a number of fascinating airship drawings, but they're not particularly organized. There's just a ten page unorganized gallery of all of his art. My favorite may will be his movie poster for the classic movie version of Lazarus Long's Airship Troopers, staring Roald Regan. :)