Artist Igor Kieryluk has illustrated thirteen Magic cards through Rise of the Eldrazi, and there's another two coming in Magic 2011.
The first step of the creation of a card's art is its art description. The art description tells the artist what the card will do, what its flavor is, and what the mood of the illustration should be. Here were the instructions given to Igor for this new water elemental
Color: Blue creature
Location: A pool or seaside
Action: This is a classic water elemental, a 10-foot-tall creature made from living water. It has a discernible head, perhaps with a normal crab inside it that almost makes a 'face' shape, but the rest of its body bends and twists fluidly, forming strong tendrils that look like they could knock you over.
Focus: The water elemental
Mood: Malleable, looming, fluid
The next step is for the artist to submit sketches of his or her vision of the art description.
Here's Igor's initial sketch.
Water Servant | Sketch by Igor Kieryluk
The creative team thought that looked great and gave Igor the go-ahead for the final version
Water Servant | Art by Igor Kieryluk
And here's what the card itself will look like inside Magic 2011 booster packs!