This is one way for you to make a pumpkin carving template.
I've found that it works best if you use an easily recognizable photo.
In a photo editing program, make your photo black and white (greyscale).
Adjust the contrast alot until the photo loses all it's shades of grey and has only black and white (two colours).
Smooth out jagged edges with the drawing tool.
Then you can decide if it looks enough like what you want to carve, if it doesn't pick another photo.
You'll have to decide if you want to cut out the black or the white, inverting the picture will help you decide which part to cut out.
One thing to remember is to make sure that your template doesn't have any "islands", what I mean by that is that there won't be any parts that require pumpkin bits to float in mid air.
Here is a second way to make a pumpkin carving stencil.
If you have photoshop, you can do it in a way that is a little easier,
make the photo greyscale.
use the cutout filter which is in the 'artistic' group of filters.
make sure you choose to make only two or three levels and then play with the amount of simplicity and fidelity until you find the look you like.
In both cases, you can invert photo or not to save ink or help you imagine what the final product will look like.
I hope this is clear enough to be useful for you, and that you have the software to do it.