This image of wild phlox on the forest floor was my first conversion from a full color image to a duotone. The original image had a few hot spots and just didn't look that great as a full-color image but I really liked the overall composition so I tried out a new action called "Duotone Dreams" (free download at atncentral.com for CS3) and this was my end result.
Canon 40D, Canon 100mm f/2.8 Macro USM
f2.8 @ 1/640th
ISO 100, early morning sunlight
Eval Meter, AWB
Handheld
Yes, it's close to being sepia but this tone seemed to be a little less "dirty" looking to me - more on the green side of things so it seemed a natural.
I too wish that front leaf would have been a bit sharper. There's always something, isn't there?