Let's look at an example art description from Betrayers of Kamigawa -- but we're not going to tell you what card is being described yet.
Show a green-aligned priestess similar to art ID #82624, as a "school" of the strange spirit-fish creatures from art IDs 80620 and 82612 swim in an upward spiral around her. The fish-things are iridescent green, gold, and blue and full of life giving energy. They're magically nourishing the priestess.
The initial sketch, created by Magic art workhorse Greg Staples, gives a sense of the kinetic energy of the final piece, but not enough detail to recognize the other cards mentioned in the art description.
Let's look at each piece of art referenced in the art description one by one, right out of Multiverse, Magic's internal card database.
Art ID #80620
This is the green-aligned priestess mentioned in the art description: the amazing Azusa, Lost but Seeking by Todd Lockwood. It seems likely we have a green card on our hands, and possibly a spell effect.
Art ID #82612
The art description points out "spirit-fish creatures" in the piece above, Jim Murray's Teller of Tales. The description means in particular the fishlike "energy objects" or "orbits" floating around the teller (which is the mouthy spirit in the center).
Art ID #82624
This is the last piece referred to in the description -- Eerie Procession also by Jim Murray. These fishlike spirits march around in an incomprehensible mystical ceremony, tutoring up an Arcane spell for the caster.
Greg Staples took inspiration from all three of those pieces to create the final image. It's a great piece!