I just found a really good tutorial on how to make a pumpkin carving template or stencil.
It comes in the form of a 20 minute video that seems pretty easy to follow. He even shows how to simulate what the final carved pumpkin will look like. I really recommend it.
Making a template to carve a pumpkin is a lot easier than you might imagine. The tutorial is for Photoshop CS3, but he doesn't use many if any tools that aren't available in a lot of the older versions. Also by watching how he does it, you could incorporate his concepts into making your own templates.
Really there are a lot of concepts that apply to making all sorts of templates that are useful to pumpkin stencils.