Real quick (I'm running out the door to get to work)

Havings rooms evoke certain emotions is likely going to be a big part of designing a home. On that note, I found an "interesting" combination.

Bathrooms are likely to have mounted fish, because you get confidence from brushing your teeth, so confidence goes where you have a sink, and the kitchen is rather better for inspiration since that enhances your cooking. Mounted fish are confidence items, so you put them in the bathroom where you brush your teeth.

Kind of icky.

That or conversely my sims would need dentures by the old age of 30, the way they avoided brushing their teeth because they needed some other emotion instead

But yes, the bathroom is a good place for Confident, since a mirror also goes well with the sink, and Confident helps with building charisma.

That said, although mounted fish are probably the easiest way to get confident decor, you don't HAVE to use those as bathroom decor. If you've learned some painting, and can get into Confident mood to start painting one, you can create your own paintings that both have a Confident aura AND act as a clicky item to give you a Confident moodlet on demand.

So basically if a mounted fish above the porcelain throne is too icky for you, you can always display some expensive paintings in the bathroom instead. And, hey, it even helps with an aspiration or two.

A noob question here:
I thought that emoting boosting decorations work only in the room they are placed in, so as soon as I leave bathroom, the "Fish Boost" is gone; therefore: what is the point?
The Fish boost stacks with tooth-brushing, but does it last after I leave the bathroom?

As I say: a noob here.

That's correct, decor switches when you leave the room. But I've only done 4 careers so far, I haven't needed Confidence for much. All I'm usually using confidence for is to fulfill the wish "Become Confident" which My sim often gets because of the Self-Assured trait.

It's like right now, I'm +2 playful (+1 Socialization, +1 Decor). If I go to an non-fish bathroom and brush my teeth... I lose the +1 playful decor and gain a +1 confidence. Result? I stay Playful. When you are tied you keep the former emotion +1 Playful and +1 Confidence remains playful. So, at this time, with these furnishings, I need the fish to get +2 Confidence to be greater than +1 Playful. That's enough to fulfill the wish to become confident.

Sure enough, when I leave the bathroom, I revert back to playful, because that's again +2, and I lose the 1 confidence decor.

However, I can disable my playful decor, and stay Confident if I choose, because the only +1 Playful from socialization would not be greater than +1 Confience from brushing my teeth.

Does that explain it? :D

+50 aspiration points for a 10 sim-minute trip to the john is good efficiency!