Halftone was the right technique! Engraving results:

That's illuminated with a pretty bright (17 W) LED bulb. I wiped some soot off the lower right of the face with a wet paper towel, which messed up the image a bit. Oh well.

I got the minimum viable product of Pumpkin Spicer ready for day 2 of Maker Faire. I just stuck a lightbulb on an extension cord inside and put the dish of wax melt next to it. Unfortunately, the incandescent lightbulb isn't really bright enough, but it melts the wax slowly: