Buildings are often built to fulfil a particular role, but over time that role may change and the building may be altered slightly, or even quite a lot to adapt it to its new role. For that reason you cannot define a building as 'a bakery' or 'a shoe shop' just because it is built a certain way, because the two can be interchanged over time. So it is less important to have set types of building than it is to have an interesting and varied set of architectural forms. For example different window patterns, roof angles - the presence or absence of dormer windows. The number of chimneys and how tall they are.
I was reading a thread about city design over at the Profantasy Forum this morning, and came across a comment I think HadrianVI made (if memory serves me right), about how he would start by imagining how the city started off life - the reason why a group of people got together and started building houses right next door to each other in that particular spot, and why it stayed important enough that it drew an ever increasing number of other people to want to live there, so that eventually shops, places of worship and eventually government buildings became necessary.
It was a very organic way of designing a city - to sow the seed and watch it grow in the imagination, and I could see how it might closely imitate the growth of real cities (which is probably why Hadrian is so good at mapping cities)
Following that principle, maybe it would be good to start off by deciding if your settlement is... for example... at the lowest crossing point of a river (as was the reason for many of the Roman aged settlements in the UK - including London), or if it stands at an important junction of transport ways. Perhaps it grew up as a port, or started life as a fishing village? Maybe it holds a strategic position and started life as a fort.
However it started out, that reason for existing will have been really important to the people living there, and will most likely lie at the heart of the settlement.
Having established that heart, the rest grows outwards from it - and that will be you making up the story of the settlement as you walk around it in your imagination through the imaginary centuries it took to evolve into what it is in the 'now' of your map.
I hope that helps some way