For my buildings purpose is the most important. What are you going to use the build for and how are people going to interact with it? These questions in turn define the tech specifications. As really in real world architecture which of course really interest me. A gallery or a mall have its special purpose. To show art or products. The tech specifications will follow to say that you can not use a lot of textures and objects in the build because they are needed for the art and the products. But you still of course want a nice space to show things.
Another question is realism. I have a tendency to put in support pillars that of course is not needed in the 3d universe. But I have found that if you follow the laws of gravity the viewers mind need not to use capacity to understand the build and can accept it more freely. Making more space to look at the art or products. I do like futuristic and creative builds but again I think it is about purpose. Do the building work as it is supposed to not just showing of itself.
Today there is another great thing growing on the graphic cards. Shadows. They affect the building and can make a big difference when I comes to make it live. I find shadows to be both a problem and a real challenge.