Color: Black
Action: Show a wide shot of an expanse of Urborg, the famous dark land where the Phyrexian Invasion began and ended. The focus of the landscape should be a huge, sickly 'blast radius' -- the place where the dark lord Yawgmoth fell. From the pitch-black center, the stain on the land spreads outward like tentacles of black mana corrupting the land. In the background can be seen the shattered remains of Volrath's mountain stronghold, now with its metal cap mostly corroded away and no Magic emanating from it.
Focus: the site of Yawgmoth's death that still poisons the land
Mood: The land is tainted with evil forever.
Notes: LINK to Art ID #3762 for Stronghold reference.
John Avon submitted this sketch:

Urborg, Tomb of Yawgmoth sketch by John Avon
The creative team wanted the Stronghold to be pushed off in the background slightly, since it's not really the focus of the card. With that in mind, John Avon completed the piece to everyone's grim satisfaction:

Urborg, Tomb of Yawgmoth art by John Avon
So what's art ID #3762, the item referred to in the art description? Surely it's the art for Volrath's Stronghold? Actually, no-it's the art of Skyshroud Archer, which happens to have a very good wide shot of the evil Stronghold in the background.

Skyshroud Archer art by Jeff Miracola