I have no idea what Benioff and Weiss have planned for the look of the series, but getting the look of Westeros right is going to be important. My hope is that they do what Peter Jackson did with his adaptation of Lord of the Rings. Early on in production, Jackson brought on board famed Tolkien illustrators Alan Lee and John Howe. The art these two did based on Tolkien’s series is what much of the look of the films is based on. So who could Benioff and Weiss bring in to get the look of Game of Thrones just right?
One of the most popular ASOIAF artists is Amok. His extensive gallery of character portraits is impressive. Certainly for costuming and casting his work could make a good basis. He also has some artwork of famous scenes in the books. Personally I’m not as big of a fan of his art style as some others, but he certainly has a very exhaustive collection of portraits so any character that would need to be costumed or cast could be referenced.
For the design of the castles and cities, they might look to Ted Nasmith. Nasmith is another popular Tolkien illustrator, however he recently did work on most of the major castles, keeps and cities in Westeros for the upcoming World of Ice and Fire book. All of the paintings he has done are beautiful and I think capture the descriptions given to us by Martin in the book perfectly. Obviously all of the works would have to be translated on screen as matte paintings or possibly CG renderings.
Lastly, we come to my personal favorite ASOIAF artist and if you’ve followed this site at all you’ve seen his artwork used frequently on here. I am talking, of course, about Michael Komark. Komark is an experienced fantasy artist, who has done a little bit of everything. His foray into the world of Westeros was done originally for the Game of Thrones CCG and more recently for the Song of Ice and Fire calendar. To me, his vision and art style captures almost perfectly what I picture most of these characters to look like in my head. I also think his skill at realistically portraying the characters and settings would help with the transition from the page to the screen. He would get my vote for official Game of Thrones concept artist.