Over time?
That'd take quite a bit of code to make it grow randomly with structure organization. Stone paths would have to be coded to go from building to building. Certain stores would need to grow only if needed. Having 2 magic shops right next to each other would be pointless. Spacing between objects and stores would have to be measured. The people of the town would need tasks that they do. Paths that they wander. Text that they say.
Sprites would have to be made for the different buildings and their ground work. There would have to be the dirt, frame, partially built, than fully built phase of each building.
A simple way I would think is:
In Tiled build a basic map with a few buildings. Add a Layer, add more buildings. Add another layer, add even more buildings, and so fourth until your town is complete. Then export each part of the build process. Then in your game have the player do a quest, after completion change the map to the map with more town built.