Here's a set of instructions for "carving" precise shapes into a pumpkin by knocking them through using a cookie-cutter and a mallet.
Place a cookie cutter on the pumpkin and tap firmly with a rubber mallet until at least half of the cutter has pierced the pumpkin's shell. (If the pumpkin shell is thin, the cutter may be pounded all the way through the shell.)
Remove the cookie cutter, using a needle-nose pliers if needed.
With a small serrated knife (or the serrated saw from a pumpkin carving kit), follow the pattern made from the cookie cutter to cut out the image, making sure to cut all the way through the shell.
TERADA MOKEI, a Japanese company, makes dense sheets of punch-out people, animals and scenery intended for use in architectural models. The sets include sports matches, mass transit, street scenes, construction sites, and an orchestra. Sounds like a fun thing to have around on general principle, for models, art projects, and entertainment value.