I found a Pennywise pattern online and I created a Pennywise snap-on face for the Jack O'Lantern found here: https://www.thingiverse.com/thing:2590046/remixes.

I also added another Pennywise snap-on. The final stl file is slightly different than the model shown in the photo. I had to make the silhouette in the revised stl file smaller to better fit the shell without interfering with the clips. I also had to poke out the eyes with a needle because I printed at a medium resolution which couldn't quite capture the eyes correctly. And I also printed these at 200%.

I used Gimp to trace the original photo and 3D Builder to create and manipulate the model. I uploaded the original Gimp files in the event somebody wants to make some changes. I'm a novice with Gimp.