I think you need to place a coal power plant, some hospitals, and some police and fire stations. =P

But on a serious note. You could try a technique similar to that used on this map perhaps. Your buildings would all be on one layer with a pattern overlay. You could use subtle colouring on the city blocks to show their function.

On that one important buildings are marked in darker squares. I once saw someone on here make a map not unlike this one, but then drew the actual important buildings in an isometric style, but not any of the regular buildings.

As for city layout I think you'll be best off deciding on what medieval culture you're trying to emulate and then doing a search for some city maps of the period for that country.