Tips for best looking graphics in fully procedural generated scene

Hello,
I'm currently using Unity as an 3d archviz output for our BIM program (think of something like smaller and more user-friendly Revit/Archicad). User can create whole houses from parametric items: walls, windows, doors, furnishing, inside/outside installations and many more.
As I said above - the whole scene is created by the user at realtime and even scene objects are procedurally generated. This means that I can't use baked or precomputed lighting and shadows - everything must be calculated at realtime.
And I'm thinking - are you guys have any tips or tricks to achieve best looking graphics calculated fully at realtime?

I'm attaching some sample screenshots to show you what I've already got.