First, here are two costumes worn by Henry Cavill as Theseus:
Next, costumes worn by Stephen Dorff as Stavros and Alan van Sprang as Dareios:
Here's a memorable piece worn by Freida Pinto as Phaedra:
My favourite of the bunch is this hoplite costume which captures some of the more creative design elements and motifs of the film.
There's also a large selection of prop weapons and prototypes available.