I think the sun is actually a good idea, since the 12 signs are based on the solar zodiac. Sun is the classical "planet" that has the most connection with the zodiac. By the way, another suggestion of what you could put around the Sun are the other 6 classical "planets" - Moon, Mercury, Venus, Mars, Jupiter and Saturn.
But otherwise, and focusing on gameplay/concept, the map presented honestly doesn't look so good to me because there are too many "dead-ends" / easily isolated areas. For example, look at Scorpio. You can protect a 21-territory area by holding just 1territory, and that sounds ridiculous to me. No, scratch that - I hadn't noticed that ALL zodiac signs are connected to the rest of the map by 1 territory each. That's egregious. I don't mean to discourage you, I think the idea has lots of potential (if there's someone who's pretty good with graphics willing to work on it, it could well be one of my favorite maps) as long as the layout is more balanced.
Maybe lay out the constellations so that they "fit" each other a bit more neatly (sorta jigsaw-like), and make it so that each constellation has about 2-5 connections to the rest of the map - both to the two constellations in either side along the zodiac, and to the planets in the center of the circle. I don't know, maybe you could use other elements to connect them as well, such as the aforementioned seasons, or even the four classical elements (since there are three signs associated to each element, maybe there could be shortcuts between them). Just throwing ideas around and hoping to help, since I think this could be a great map if gameplay and graphics are well-designed.