A couple of years ago I was asked to paint a new cover for a reprinting of "Young Death, Boyhood of a Superfiend", which was the first story I ever drew way back in 1990.
Here's the cover I painted from scribble to finished piece.
First the sketch
Then I drew a tighter version was then, scanned and printed it out in blue over which the final tighter pencils were drawn.
This was again scanned, the blue removed in Photoshop and the lines were coloured, as I thought it would help to make the background recede a little behind the figure and as I was painting the final version I felt a coloured line would be less harsh against the watercolour.
The line work was printed out on a hot press watercolour paper using a friend's Epson that uses waterproof pigment inks. This was spray mounted to a board to ensure it didn't cockle when I ladled on lots of water during the painting process.
The image on the left below is a scan of the finished painting, the image on the right is slightly digitally enhanced---I dropped a multiply layer over shadow areas to give them a little more bite and increase the contrast.
And the final image with a cheesy border befitting the tone of the story.