I nearly fell asleep several times while watching this film. Only the costumes, Ioan Gruffudd and Clive Owen kept me in the cinema. I'm of the old-school of Arthurian legends, and this film wanders off in a different direction. But anyway, the costumes are pretty. They were designed by Penny Rose and I found some new photos of the archer dress and the wedding dress which Keira Knightley wore. Costumersguide have lots of photos from when they were on display at exhibitions and previous sales on prop store.
I also thought you might be interested in the costume maker's website - janelaw.co.uk. Her team have worked on many films and it's well worth looking through their gallery as the skill of the makers there is first class. Their King Arthur gallery is here.
More photos under the cut...
The Archer Dress
There are some nice details such as the eyelets and beads running down the slits in the sleeves, and I love the texture of the fabric. It looks like there was a fair amount of hand sewing details, such as the stitches on the armscye. As a hand sewing nerd, this pleases me muchly.
Prop store have it listed as a "rough pale turquoise cotton". I would have put a fiver on it being wool, but consensus is that it's a homespun cotton. I think that it's been cut on the bias so that it drapes beautifully.
screencap credit: ladymason