Hello, glad you liked the app.
Every race defined in the generator doesn't use all possible combinations of body and heads because I thought that it looked weird (for example, a skinny minotaur). However, by editing the race files (*.race) that can be done (Hope I understood your question).
Regarding the owl head, I haven't found any yet. If I do, I'll gladly add new race for it.
Also, the Godot Addon sure is a sweet piece of work. Playing With Godot might took some inspiration from this app, but it stands on it's own now and you can only praise his work.