Some suggestions
1) Skulls from other animals. I imagine "raven", "shark", and "wolf" would be popular
2) They don't even have to be skulls. A highly stylized wolf's head, although just about any predatory animal would have a following.
3) Remember the Guns N Roses skull from Appetite For Destruction? I don't know about intellectual property laws, but it would be a cool throwback.
4) A Voldemort skullie
5) And Darth Vader
6) Sauron, although there may not be much crossover between these two cultures.
7) Cthulu, for those of you who know what I'm talking about. A complicated job, though, what with all the tentacles.
That's all for now. I'll post if I think of more.
Yeah, I thought of more.
There is a Darth Vader skullie.
Some suggestions for other materials to expand the "wabi-sabi" line.
1) Carbon fiber (of course)
2) When you're ready, some made out of that nitrogen-based steel, so that they never, ever, rust.
3) Also, some made out of tool steel so that they do rust, or, "patina", if you prefer.
I also thought some cyborg wabi-sabis would be neat, with robotic eyes and an assortment of tubes and hoses, maybe some metal teeth.
One that I would like to see is a fully robotic head, built in a more 19th century style, so that the parts look riveted together, bolts are exposed, and there are fittings, valves, and other essential machine bits. For the extra special touch, it should look like it has had a refit or two, with clearly add-on parts, and a nice layer of "use rust".
JACK SKELLINGTON!!!
And a Green Man wabi-sabi. For the proper touch, use Ash wood.