Can you design your own evil enemy Unit to a given theme? A Unit you will need to fight or a boss for this theme? Why not entering the Enemies Contest? Submit your very own idea as an image file. If you have a good design it could happen, that your idea gets added to the official game in a future update!
You could draw an image of the enemie digital, paint it on paper or handcraft it with whatever comes to your mind. Creativity is everything!
It just needs to fit the theme above!