I'm a bit unsure over some of the cast members also. I imagined Clary to have more vibrant red hair than Lily Collins who has been chosen as the part, who has brown hair with a tinge of red. I also was disappointed with the choice of Jamie Campbell Bower, apparently Alex Pettyfer was offered the role and he turned it down and I would have thought he would have been better for the role. I'm not sure either of Kevin Zegers who has been cast as Alec. Valentine and Isabelle are exactly how I imagined however. I'd say the rest of the cast will come together when I get more used to them while watching the film.
Also I really hope it follows the story of the book and doesn't cut important or my favourite parts out. I think it'll definitely be worth a look. Check out the trailer below: