Hugh Laurie would be perfect for the role of Thom Merrillin.

Rosamund Pike is a great choice for Moraine. She is taller than in the books, but that should not be an issue. Her height never really plays any significance in the story. Cairhien does seem somewhat like France...Just look at the book covers for more clarity. 

I think the first casting will be for Moraine, Lan and Siuan Sanche. I believe the series will begin twenty years before the Eye of the World begins, when Moraine and Siuan Sanche realize that the Karaethon Cycle prophecies have begun and the Dragon is about to be reborn.

I think Jason Momoa would be a good choice for Lan 

On ‎2‎/‎17‎/‎2019 at 7:08 AM, Elgee said:

I think the first casting choice should be for Moraine and Lan as they will be the lead storyline to begin the series. I predict that they will be established actors, in that Amazon will want big names to launch their epic show. It will be a large ensemble cast made up of big names and fresh faces. The casting director has a big job ahead of them. We should here something about casting choices in the next few months.

 Now that it has come out that Wheel of Time will start filming in Prague in September, when will casting begin? We are six months away from filming, who will be cast first? I think Moraine and Lan will be the first to be cast. In that the series may go for 10 years, they must cast actors who are willing to commit for up to a decade. Could be lots of new faces...