Here's the art description:
Color: A location associated with black
Action: Show a bustling, black market bazaar that is occurring in Ravnica's undercity (see pp. 14-17 for examples of the undercity). Various unguilded humans, goblins, and ogres peruse wares here (see pp. 193-197 for examples of unguilded Ravnican costuming). Maybe some shady-looking merchants offer stolen blade weapons. Some vendors could sell cages of illegal exotic fantasy creatures. Maybe others carry baskets of strange, fuming potions.
Focus: The underground bazaar scene
Mood: A dangerous marketplace for the criminal element
And here are the three sketches the Creative team had to choose from!

Underworld Connections | Sketch by Yeong-Hao Han

Underworld Connections | Sketch by Yeong-Hao Han

Underworld Connections | Sketch by Yeong-Hao Han
They all look like they could be pretty great. The Creative team decided they liked the wider shots seen in the second and third sketches and asked the artist to choose. And this is what they got!

Underworld Connections | Art by Yeong-Hao Han
And here's how it looks on the card, as seen in Return to Ravnica packs.