I've done a carving for My Neighbor Totoro and Princess Mononoke. I had one more character from a Studio Ghibli movie planned which was No-Face from Spirited Away. However to make him work, I had to mix colors. I tried it before with Shiu Pei's owl. It wasn't easy but hopefully I learned from that. It was simple to carve the body out a black crayon. I melted a white crayon using my special tools to apply the mask. I placed a base layer which sometimes melted the black causing black swirls in the white. Luckily, applying more white on top was fine since the black swirls were unlikely to melt again since there were so little of it. With the mask applied, I smoothed it out and then carved in the face and markings. Unfortunately, it was hard to make out those features. So I melted a purple crayon to apply the four markings. The eyes and mouth holes still looked faint though so I smeared some barely melted gray wax into the walls of the holes (not filling it though). It turned out well although after I was done, I brushed everything off and black crayon dust in the brush got stuck on the white mask making it not pure white anymore.
Here's my trio to represent Studio Ghibli. Below is a picture of the characters if you're unfamiliar with them. I was too lazy to get three pictures and Photoshop them together so it's just someone's drawing that happened to included the three characters together.