100,000 is not impossible. 100,000 in 25 years probably is impossible (magic not included). One of those things will have to change, or a non-realistic explanation created. rdanhenry is also right - somewhere between 10-30,000 is also quite plausible.

Waldronate, I should probably clarify what I mean by suburbs. I don't know how widely known this is, but in archaeology we often use the word suburbs simply to refer to the parts of a city outside the city walls. When I said 3/4 of the population could be outside the walls, I really didn't mean the suburbs that proliferate in America and Australia.

I also didn't mean to suggest sprawl. The people living outside the walls will live in fairly densely packed clusters.

The main point I wanted to make is that any city of this size will have many poor people, and probably some large slums; but no planned city will ever include slums as part of its planning. So, the poor people will come, and settle outside the walls. Their access to building materials will be limited, and they won't be investing in high-rise apartments. The houses would be much more haphazardly built, probably only one storey high (two at most) but also very tiny. The density would come from the smallness of the buildings rather than their height.

I once heard that in Istanbul in the 1970s(?) the government wanted the city to grow. The policy they came up with was to say that if a person can build a house on some land, that land would belong to that person. This resulted in lots of poor people from the countryside arriving at the city with all their friends/family, and putting up cheap shacks overnight. There was no planning, no laying out of roads or infrastructure. The best places were near existing roads, but, naturally, houses spread out from those. That is how I imagine the 'suburbs' of this city to look.

I may have used the word sprawl, though. What I meant was houses that spread (sprawl) along roads. Sometimes they will cluster, and sometimes they will be sparse. Sometimes they will form separate villages. As a caravan gets close to the city, it might be near dusk, and so rather than going to the gates, they'll stay at an inn. That means you'll have some people who set up their homes near the inns to try and sell odds and ends to the caravaneers etc.

The multi-storey apartments that Waldronate mentions are quite plausible for inside the walls, but I suspect they would have a higher class of resident living in them.

The wide boulevards I agree with. I originally posted a comment where I said that the European Baroque developed the notion of wide avenues quite late in history. This is not entirely accurate. Major avenues leading to important parts of a city existed in Roman, Egyptian, Chinese and Mesoamerican cities, but they were mostly processional ways (places for armies to make triumphal arches, or ritual events). The Baroque simply modified the idea substantially.

Mornagest, that map of Lyons you found looks like a Braun and Hogenberg. They were mapping the cities of the world between 1572 and 1617. The style they use is quite indicative of that period in mapping (and they are works of art in themselves). I don't know how good you are at drawing, but I doubt anyone on the guild (with perhaps one or two exceptions) could rival that type of thing. It might not look as pretty, but I'd recommend you stick to top-down images, and follow Midgardsormr's advice.