I can't believe how nicely this turned out and how easy it was:
Here's the original portait:
I converted it to greyscale in photoshop and played with the threshold - here's what came up with (keep in mind, I know very little about photoshop - that's how easy it was)
My husband did the carving - I love it!!!!
Edited to add: Just to expand on my tute a little bit, we printed out the stencil and taped it to the pumpkin...then we used a really sharp pen to poke throw the paper along the stencil lines and make marks on the pumpkin...then we removed the paper and drew along the dotted line in pen just to make the carving lines stand out more.