Hm...
Basically, a very fine map. I love maps in this style, and this is a great example. I like the very subtle colouring and I admire you for the level of detail that you put into labeling all these cities.
Yet, I think there are a number of things that really could be improved and transform this fine map into a really great map. But I fear - if you come to agree with my points - it will be a ton of work for you.
1. Composition: it just looks unbalanced.
The focus of the map is, as the title tells us, the "City-State Union". Yet these only take a tiny fraction of the space of the whole map. About half of the map - the whole western part - is just empty sea. Even with this inset-map, you could do away with a quarter of the map.
2. The inset map: placement and content
The position of the inset looks a little arbitrary... this comes, in my opinion, from the whole flawed composition and all that empty map that is there to fill. If you were to place it on the border, as it usually would be, there is still to much empty space.
My idea: make the inset bigger - a lot bigger. So you could use all that empty space without having to resize, trim or redraw your whole map.
You could also add a lot more detail to the inset map... that is another of the things that bothered me a little: there isn't that much more detail in the inset map over the island shown in the big map that an inset would be justified.
3. Labels: limited readability
The way of placing your city-labels along the coastline is rather good and it is fitting the historical style. But you should try to have your labels not overlap the coastline - this makes them harder to read quite often.
You have enough space: just pull them outwards a little.
4. U and V: what is what?
I guess you go for some kind of old latin touch by replacing U with V... but as you still use the lowercase u, it can get a little confusing. If you are not set, for reasons of style, on the U-V exchange, I think you should drop it completely.
5. The coats of arms: too much
They are great, and I can understand why you want to use them as much as possible. But the small coats of arms within the map body (depicting the capital cities, It seems?) do not really fit. The hide other map elements - never a good idea. You could use a bigger version of your city circles to show the capitals.
6. the rivers: too branched... or not enough of them
While the main rivers look excellent, the many branches of the rivers shown suggest that even very small tributaries of major rivers are shown. But in that case, there should be a lot more of shorter, smaller rivers be visible on the coastline. These fractal, bushy structures just don't look realistic. Check some real world maps to get some ideas.
7. the paper texture: too heavy
A question of taste: I think a little less opacity would be better.
8. the border: no texture
Well, just that: the texture is the paper, the medium on which the map is printed / painted. So the border should also show a paper texture, shouldn't it?
9. the rhumb lines
Again, a matter of taste. The lines themselves look very good. But personally I think that you should consider exchanging them for a graticule - of whatever projection you like. It would emphasize the more-modern style of the rest of the map.
10. Don't kill me!
This was quite a list, wasn't it? Don't take it too hard: I really like that map... that' why I want to see it perfected!
And I would be very interested to hear what you think of my critique.