I'll let you change the numbers as necessary to fit your pumpkin, but here's the general rundown of how you'd make this beautiful decoration in the free student version of Autodesk Inventor 2013:
1. Start with a hexagonal prism that's hollow and doesn't have a bottom. Make the sides using lithopanes generated from the link in the first paragraph during actual assembly if you wish. Make sure it's small enough to fit into a whole in the bottom of the pumpkin.
2. Using the Design Accelerator feature, create a pair of bezel gears. You'll probably want to gear them for speed, but if your pumpkin size doesn't allow that, just make the ration 1:1.
3. Create a basic drive shaft with simple extruded sketches. Attach a handle and be sure to make the whole is thing long enough that it fits out of the pumpkin.
3. Make the proper rotational constraints on the gears, lithopanes, and drive shaft in the assembly mode. The gears should meet at a 90 degree angle so that the handle comes out of the pumpkins side, while the lithopanes spin inside the pumpkin. (see the picture). One gear should be directly attached to the lithopane hexagon, the other to the drive shaft.
4. If you aren't using a real pumpkin, it's time to design that too. Create a new object and a 2d sketch. Draw a crescent, and use the revolve feature to make one "slice" of the pumpkin.
5. Fillet the edges of the slice. These filleted edges will meet to form the lines which run up and down the pumpkin
6. Use the circular feature tool to rotate the slices along one central axis to close up the pumpkin's sides.
7. Add a cylinder for the cap, and use the follow path tool to extrude a circular sketch into the shape of a stem. On the underside of this cap, add an axle for the gear attached to the lithopanes.
8. Cut a viewing window to watch the animation. Chamfer the edge to make it look pretty.
9. Scale the pumpkin as necessary to fit the gear assembly. THEN add a whole for the drive shaft. Use the assemble tool to piece these together.
10. Put some form of LED candle under the pumpkin so the light source is in the center of the lithopanes.
11. Turn that crank like there's no tomorrow! Or add a motor! Or turn the gear into a geneva mechanism and make it a slideshow! Get creative and have fun!