Not an expert, per se, but I don't think there's a common practice. It's a matter of taste. I think in a smallish room like a bathroom with a cathedral ceiling, I'd be inclined to paint it the same color as the walls. I think it would make the room look more spacious because you wouldn't see the different blocks of paint like you would if you painted the ceiling white. That might not necessarily call attention to the architectural interest, though. If you're not sure, go ahead and paint the ceiling white (shouldn't take that long in a bathroom), then paint the walls beige. If you like what you see, leave it. If not, just paint over the ceiling with the beige. It would be easier doing it in that order than painting it all beige, then having to go back and do the white ceiling. Sound like a neat room and it will be nice whatever you choose.

Your ceilings are not really that high, don't worry about decorating all of the tall wall. I read here once that if you decorate nicely at the people level, your tall ceiling will make your space look nice and airy, not bare. I would do one or two big items like Olychick posted, there is not need to decorate the whole wall. Add some texture, color and height variation to your side table and coffee table and it will help anchor your "people" space.

I love painted ceilings, and I'm finding that white vaulted ceilings in my house look odd with painted walls (so most of my walls are now white to blend the two together). That said, I don't have any beams or trim or lights on my ceilings to contrast, and my vaults are steep enough that the ceiling looks more like an extension of the wall. With your lower vault and the beams and the lights, I'd be pretty tempted to leave it all white. If that last picture is your bathroom ceiling it looks small--is it a powder room? If that's the case, I'm all for doing something really fun.

Hi. Good idea to change up this decor, as it feels incohesive and lacking texture and color (if you want that). When designing a room, it is critical that you take these steps. 1) Find and post for yourself and for this post: photos of rooms that you like. You cannot proceed or ask for help until that step is completed 2) Decide furniture. This is based on #1 as well as the measurements of the room and rooms around it. So, a floor plan is critical as well as 4 photos of the room. 3) Purchase furniture. 4) Decide art and decor. Can you skip any of these? Yes, but your room will be compromised. Not something you want to take on? Hire a designer. Good luck  😀