I did some doodling for fun about glaurung, and of course this is a lot more cartoony than the realism needed for film adaptation. I tried to find a balance between "facial expression" and believable dragon but I think I didn't quite pull it off, its too much like a character for animation. But I still think Glaurung should be something of a real character, not just a particularly big and scary beast. (although I like the idea of a very bizzare monstrosity like that roger Garland one but I have the impression that would be a challenge to make that one into a real sentient character)
Here I've drawn him quite smirky but I'm actually not sure, is he very "earnestly evil" or does he kinda have a "playful/mischievous side"? What I wanted to get at is that I imagine him to be able to be expressive, so there would have to be some "human" influence in the facial expressions.
Also I'm not sure about the body type, which basically, as all of you have discussed already, is about what animal to pair with "dragon attributes" I'm personally leaning away from the tank version/giant heavy reptile (very heavy beast that'll squash/bite everything to death) and more towards a heavy but agile, very fast and strong creature that'll attack explosively, and is kinda already a prototype of a winged dragon, just from how it moves and what its strength in combat is. Then the wings would be an upgrade and not a complete 180 turn. So the ones that were proposed here are very reptilian, with legs besides the body and very long, tube like bodies, but I wonder if you could have a dragon that has a bit more of a runner-build, that could actually sprint... he would have to, right? Otherwise I kinda have trouble to see Glaurung as giant force he is. (but still very intrigued with the roger garland drawing, but maybe there could be some "mutated" version of a more mobile creature). I think nobody really wants the snake dragon, they are fun to draw but tough to imagine playing the Glaurung role.
Also a question I thought of: What do you reckon how fire breathing works in this world? Is it the GoT style giant flamethrower, or a bit more subdued, or is it very hot air that sets everything on fire, or some kind of magical fire? How hot is it about? Not that important I was just wondering.
anyway just things that went through my head while I was doodleing.