A D300 in-camera Image Overlay - two images of the same flower (a double exposure), one in focus & one totally out of focus to provide a soft halo-glow effect.
For an "arty" B&W conversion see - http://www.pbase.com/ed_k/image/98465171
I love the play of diagonal -- I mean "oblique"! -- lines in this image, along with the harmony of shapes and colors.
Using the D300 multiple exposure setting, I've not yet had much success with the Orton effect. I suspect my DOF has been too deep, but wonder... Have you found Image Overlay works better?
A really interesting technique. I have a D80, so I'll have to check to see if double exposures are allowed. Thing so. But I'm not as adventurous as you are.