Yeah Merry Christmas and happy new year!
Was thinking about your Zodiac work and I think the Pisces one is the most successful because it has some medium ground with the stark lines crossing over the colour part at one point. Think this could work for other pictures in the same style, like if your blending two colours you get that middle tone bit. In the same way visually that could work with the colour and lines. Not sure if I've explain that very well :S lol
Anyway hope that helps in some way.