You could tighten the space between territories, but keep the larger gaps between bonuses. I did that here:
And it gives it more visual definition. On mine it was needed to have the larger gaps though because the colors are similar (as they make up part of a larger super bonus).
Either way, yours are not consistent (some are tight, some not). Cleaning those up would add a lot visually.
You could add a brick like pattern to the stone walls maybe.
Also, I see no reason why many of your bonus links can't be within the bonus themselves. Not all (like explosive mines), but most can be. I prefer them within myself, but others may prefer them surrounding edge like you have it.