I'd like to default to "if you created the NPC/location, you describe how it looks." Of course, someone may have connected your creation somewhere along the line in a way that might change your initial thoughts, but everyone here seems to be pretty collaborative so far, so I don't see a problem with making adjustments to fit the setup.
Please do tell me if there's a detail like that, big vs small lab, someone looking scary or attractive, or really anything that you pictured for your NPCs or locations. I have ideas, but they may not be like yours.
I'd also like to stick with the "once written, it is truth" default so that if you make up a detail in game, it becomes fact. Some things may need changing, but I'd like to default to the "what's written is law" bit as much as possible .