How about the uniforms from Vampire Knight? They're Black & White with a tie and dress shoes. Somewhat formal. Here's a pic for reference: http://fc16.deviantart.com/fs31/f/2008/215/8/2/Vampire_Knight___Zero_x_Kaname_by_j_b0x.png (I will be going as one of the chars, and my friend as the other.)
Alternatively, Suzaku Kururugi in his Knight of Rounds costume: http://that.animeblogger.net/2008/05/10/suzaku-hero-of-the-soldaten-long-post-about-why-suzaku-is-not-evil/ (top photo)
Alternatively, Suzaku Kururugi in his Knight of Rounds costume: http://that.animeblogger.net/2008/05/10/suzaku-hero-of-the-soldaten-long-post-about-why-suzaku-is-not-evil/ (top photo)