I just want to throw this at you. (I hope you're good catchers. I'm sure you are.) This is for spending detail on setting up sets/houses for storytelling purposes, contests, or just because you can. You may or may not need this advice.
Here's a little MDP trick when it comes to building and decorating a house...stop thinking of it as a house. Think of it as separate rooms designed to meet the needs or likings of those living in there. Because you can concentrate on little details more easily when you're not trying to bake the big potato. Bake little potatos seperately in their own little foil wraps. It's much simpler.
For instance...you've got a three bedroom house, 2 bathroom, living room/dining, and kitchen (maybe hallway and a foyer in there as well), and a family of 6 (2: parents, 2: twin teenagers, 1: kid, 1: baby, maybe on the way).
Now for themes you're on your own. I don't really believe in "complete" theme houses. Because buddy, my parents like rustic/western...I don't...so my room isn't going to be in "their" theme. It's going to be whatever style I'm into.
So the parents, of course, get their own bedroom. Depending on the parents, there's going to be relics and pictures of their past times and maybe some pictures of their children (I say if you're going that way, pictures of family and children go in little hallways or the living room where it can be observed more closely). The bedroom spread is probably going to be more to the mother's liking, but not too girly that the husband wants to sleep on the couch. (Well, unless the husband is the decorator that is.)
A little more "grown up" feeling. But also, I think more importantly, the room will be pretty much empty. All the clutter is spread throughout the rest of the house, why not have an empty room to sleep in? So whatever to the parents liking: dresser, walk-in closet maybe, full length mirror and/or vanity table, bed (of course), end tables, dim-lit lamps, and a decorative plant because who can live without one? Maybe Dad's shoes thrown in a corner and Mom's shoes spilling out of the walk-in closet. Whatever the circumstances, show a little character. This couple has been together for awhile, they live with each other and probably fight about every little sock on the floor so throw those decor socks beside the laundry hamper.
Ahem.
Twin Teens, sharing a room. Oh boy, depending on your teens you may have a radical one and a neat freak. I really don't think I've ever met twins that were EXACTLY the same. There's always some difference in personalty. For example one teen likes country music...one likes hip-hop. Throw up them posters like they're having a war! Colors are the best way to show the difference between teens. One likes red, one likes sky blue, different bed spreads. If you have just a plain square of a room, the two walls that connect the seperate sides of the room should be some neutral color while the other walls are painted to the teens liking. The West side of the room is red...well the east side is sky blue. This also marks boundries if you're twins are sick of each other and are fighting over who's turn it is to take a shower.
[Recalculating]
Now the other bedroom is for the kid and baby. It's your average "I'm a kid. I'm messy and have more toys than I know what to do with." That is, depending on your kid. If the kid be a neat freak/bookworm...I know there's plenty of books to download so he/she can be happy.
While that side of the room may be a complete car wreck...the other side is getting ready for a tiny baby so there's going to be gifts, a crib, changing table (if you believe in those things), and whatever else you believe is baby worthy. I personally don't make nurseries all too often, but when I do...they are always in neutral/soft colors because I don't believe that girls should wear pink and boys blue.
Bathrooms are usually a pain in the ass because there's only so much you can throw in there, but main things like toilets, maybe a stand up shower for the teens and kid...sink and counters...oh yeah and mirrors. Teens are going to need hair dryers, maybe straighteners for girly girls, make up also...the kid may have a stepping stool, colorful rug, duckies, sick shit like that.
Master bathroom is not only the luxury item with the awesome big tub, but somtimes can double as the laundry room...if your bathroom be big enough. It should show a romantic/soft setting, towels neatly folded, and again depending on your Sim, pretty much empty. Sure use a rug to make the space not look so big...unless you like small Master bathrooms. I'm not against it.
[Inhale and Exhale]
As for the rest of the house, it's up to whatever theme you picked out. I like contempery...but not too moderny...just casualnessesses. Also remember that people live there...so it should look like people live there. Stuff thrown around randomly, briefcases, shoes, glitter, paper, counters filled with food, appliances, and homework due three weeks ago.
I mentioned the possiblity of an entrance way/foyer...probably one of my most favorite parts of a house. There's gonna be all kinds of stuff there: soccer balls, bat, hats, shoe rack, umbrella, coat rack/hanger thing-mabob...a welcome mat, light switches, security alarm thingy, and I'm a firm believer in a fallen down painting because of how many times those damn kids have slammed that damn door. Just sayin.
Outside also needs characteristics...a car that matches the income of the family...considering it's a family I don't expect to see just the nice muscle cars...there should be a van or station wagon, maybe some type of SUV.
If the house is shabby-ish (13pumpkin) or just old, vines are always a must. Maybe Mom or Dad is a gardener, or the kids
need a pool...floats and lily pads...I don't know why, but I like putting lily pads on pools. Try it out, say what you think. If you don't have a concrete driveway, take some dirt terrain and give yourself a muddy/dirt filled mess of a driveway with or without the skid marks.
I'm not saying you have to or should use this advice, you don't, but I believe the house or environment you're around or in, should show a lot about your character, thus, my (real) room is a mess and so is my self Sim's.
This can also be transferred into prose writing. Visualize and describe how you see your character...their room should look pretty close to what they do. Should, but not always.
Get it, got it, good. Have a nice day. Cheers.