I was sitting in class at City College once, not taking notes – drawing instead. One of my peers looked over and asked what I was doing. I turned my book so she could see a sketch of one of my favorite main characters.
It wasn’t enough for her. “Who’s that?”
I told her and she asked, “You draw your characters? Why?”
Now it was my turn to be confused. “Why wouldn’t I?”
Writers are taught that in prose, it’s a clever tactic to leave the physical appearance of characters to readers. Give them guidelines – simple descriptors that create an image of the kind of person someone is. You could say, for example, that Rock Stout had golden hair, perfectly curled, and wide teeth that almost glistened when he smiled they were so white, and from that we’d generally get that Rock Stout was an ass – or probably an ass.
The same occurs in Fantasy writing. The simplest description in the world is “he had a chest like a barrel.” I’d almost be worried about quoting someone specifically, but this has been said in so many ways in so many stories that I believe it’s impossible to quote anyone specifically with this, and – furthermore – I’m not saying this descriptor is a bad one. The point is, we get everything we need to know from that phrase: this man drinks, laughs loudly, probably uses an axe or warhammer, probably likes wine and whores, is possibly a black smith. It’s simple – about as simple as Rock Stout’s description. Likewise, our hero can be simply described as “usually the tallest head in a room” and again, we get the idea.
The question then is, why bother doing more than this? Why devote as much time to character design and artistry for a media that barely needs it?
The answer is simple. Because I don’t want this to happen:
This is the US cover of Robert Jordan and Brandon Sanderson’s The Gathering Storm. And, sadly, it’s probably the best cover for the series so far, or among the best.
Now, let’s see what happens when, Seamas Gallagher, who takes his time and, more importantly, cares, renders Rand Al’Thor:
So, what am I saying here? Is it that all fantasy writers should spend time trying to draw and design their characters? That even if they do, the artists assigned to do their cover art somehow will – or will even try to get it right? No. What I’m saying is that when War of Exiles is released, if it has a cover that looks as off base as this –
– you can come back here and look at the awesome character sketches and art that I’ll have up by then until the pain stops and the tears go away. Mine and yours.
House of Error 
I always heard the advice that, as writers, we should leave details of physical appearance out so that the reader can easily put themselves in the character’s place and imagine themselves within the story. I don’t know about everyone else, but I don’t have the best self esteem when it comes to the way I look. I read books to get the hell away from myself for awhile. I want to pretend I’m someone else.
As writers of fantasy, we strive to paint originality in every form, be it plants, creatures, weaponry, cultures, and people, and then that advice tells us to stop short of a character’s appearance. We can tell you what they’re wearing, their build, and the color of their hair and how they wear it, but their face is OFF LIMITS. Writing about blank slates might work for romance novels, but I don’t think it suits fantasy. Just my two cents and long-winded way of saying I agree.
Thank you. : )
Actually, come to think of it, the other day, an artist asked what movie or game character Lethe looked like with his hair and everything, for visual reference. It was hard to grasp that there wasn’t one–I sat there thinking for a while before I reminded him of an ex-girlfriend who had strong features and was really pretty. I said, “Like her. Only not pretty. Also, a boy… Well–just, strong, square-ish face, strong jaw–but handsome. And not a brute.” And then, “Think of a lion,” which I’m sure didn’t help at all.