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 Ron was given for Darksteel Gargoyle:
Color: Artifact Creature
Location: Inside the "Lumengrid" in a secret chamber
Action: Show a darksteel gargoyle atop a pedastal that can become animated when charged with mana.
Focus: The Gargoyle made of "darksteel" magic metal
Mood: Wait ‘til I come to life
Armed with that art description, Ron submitted a sketch to Magic's creative team, complete with annotations.
The sketch was approved, and here's the final result.
Here's what it looked like in Darksteel packs: