If I get the inclination I'll go back and add smaller sizes. Given how old this one is, it seems a bit unlikely at this point.
The license on these is open for a reason, if someone wants to take what I started and expand on it or use it, they're more than welcome to. I'm overly excited with how this one came out, and would rather move on and try new things than spend time trying to make this subpar icon work at a smaller size.
For this particular icon? A combination of the following: I really didn't wind up using it much myself, I was somewhat dissatisfied with the results, and I'm not entirely sure it would translate well to lower res icon.