My understanding of the exciting world of illustration is that clients usually receive an agreed number of sketches. Their choice provides the basis for the illustrator's final artwork. That's what I have done on the few occasions I've done artwork for clients. I hope I get more chances someday.
Tonight I started work on an idea Jennifer submitted: a black and white t-shirt graphic with Miss Havisham from Great Expectations on it. This is my first sketch: a broken-hearted Miss Havisham, jilted on her wedding day, never to set foot from her house again.
The tone and style don't yet fit but the great thing about art is that you just keep doing it until you get it right.