Here are some pen and marker sketches for the cover of James Blaylock's 1984 science fiction novel "Digging Leviathan." Blaylock was one of the originators of the "steampunk" movement.
The fish-shaped digging machine was made from spare parts found around the house: a garbage can, a roller skate, a brace and bit, a bicycle, some shovels, and an old umbrella. The character was inspired by the "subterranean prospector" device that he read about in E. R. Burroughs' novel "At the Earth's Core."
While still in the idea generating stage, I find it helps to draw something over and over again, because each time new ideas emerge. The final cover was a combination of the best of these sketches.
--------Previously: Digging Leviathan, showing an unused color sketch.
Wikipedia on "The Digging Leviathan"