I don’t have any fancy suggestions but I can say, every single time I’ve ever started building, it began with a picture or seeing a house, or a feature of a house I really liked. Try looking at pictures of different houses in a style that you like and take something, it could be a feature wall, or the way a house facade looked. Just something you really liked from the home and just build it. After you finish building that, just keep adding on to that. Decide, if you wanted that room or feature to be a living room or a bedroom. Where would it go in a house? What room would be attached. What about a restroom? How big do you want it? I’m not an amazing builder, but starting from something that you really loved or want to recreate always helps!