George R.R. Martin describes his vision of the Iron Throne on his blog.
"And yet, and yet… it’s still not right. It’s not the Iron Throne I see when I’m working on THE WINDS OF WINTER. It’s not the Iron Throne I want my readers to see. The way the throne is described in the books… HUGE, hulking, black and twisted, with the steep iron stairs in front, the high seat from which the king looks DOWN on everyone in the court… my throne is a hunched beast looming over the throne room, ugly and assymetric…"
These amazing paintings created by the talented Marc Simonetti depicts Martin’s Iron Throne, and is a rough draft of what you’ll see in the next book, The World of Ice & Fire.
You can find the whole story as well as Martin’s blog here.