I had pictured Brienne along the lines of MMA fighter Gabrielle Garcia (6'3" 240 pounds or so) than Gwendolyn Christie. However, Christie does look pretty good in the role, and I doubt there are many actresses as big & thick as Garcia.
(some pics here: http://womenprofile....lle-garcia.html )
You know thinking of George's physical description of characters, or at least my take on it, is that it's kind of 'cartoony' .... meaning in reading the novels I got ideas about people's eyes, and a this and that thing about hair and a little other stuff, but in general nothing seem detailed enough for me form a mental image.
I think I have seen this in the artwork that was done before the HBO series.
I must have seen , maybe 10 Brienne illos, none of them alike.
I wonder how the artistic representations will proceed now?