I don't know the history, setting etc. of your campaign, but your wip intro sounded very promising. I even don't know the scale of the map, but some of the clusters look very detailed, so I think it is a very big city.
Here are some of my thoughts:
- I'm not a fan of the american city layout, but here it makes sense and fits to the setting
- I miss the spontaneous WOW effect so far. The shape of the city could also be an xy city and it is not necessary in a higher technology level to place it next to a river. So there it is a dwarven city it could be completely built into a mountain (steampunk Moria) or just a part of it and the other outside.
- Have you ever played Sim City? I mention it, because you wrote of a steam railway system. Try to implement a railway into a finished town layout that's fun.
- With a high technology level the city expands in 3 dimensions. Not just x,z also in height. You could map e.g. a 3 level city: ground level (poor ones, because of gravity), mid level (50-100 meter, workers, transit system etc.), upper level (100-150 meter, elite, parks, art, monuments etc.)
- some important places can't be generic and should be drawn individually
- the style you chose is an abstract one. This works fine for medieval societies, but I have a problem to imagine it in a steampunk setting. So much is possible there, may it be the transportation system or architectural wonders.
Ah, and your question: have a look at the most detailed cluster you have created. Without a scale the city must be enormous and this level of detail is the base for the other blocks.