I'm not a mother (but I am an aunt to 6 kids) so I guess take my ideas with a grain of salt. I'd go with some sort of adult lighting which complements the space (perhaps one hanging fixture, or a row of them on the beam?) And, add in some table lamps to make it cozy. I would think the main goal would be to make it nice and cozy for a small child. My view is that the decor should be functional and should not have to be changed out as the child grows. You can bring in the "fun" stuff with linens and other accessories, rather than getting a bunch of stuff a fickle child might not even like down the line (or appreciate at age 2 1/2) and which you'll just end up getting rid of. Then again, I have never really understood decorating children's rooms or nurseries in strongly "child-like" or baby colors and themes. ;-)

Cubes where the room is not wider or longer in at least one direction than the ceiling is high are not particularly comfortable, similar to how large rooms with low ceilings are not particularly comfortable. In a cube, the room tends to start feeling shaft like, where a large room with a low ceiling often seems to sag or press down in the center. Also, cubes are static and rectangles are not. It might be better if the ceiling was 15-16 if 24 is the largest dimension of the room. Peaks are a little different. I lived in an apartment where the original parlor floors were essentially a golden rectangle. They had been lofted at one end (about 1/3 of the space) and it made the high ceiling in the remaining area kind of elevator shaft-like. The apartments that maintained the original proportions were more comfortable spaces. Of the above pictures Mutiny and Rufty seem fine because of the length of the room and the ability to experience the height from the opposite end of the room in some sort of perspective. I actually find the Shades Creek kitchen proportions unpleasant. It makes a good picture but I don't think I would like working in that kitchen. I am curious as to how many people with 8-9 foot ceilings vacuum or clean them on a regular basis. I am not sure the extra height makes rooms extra dirty? That said I had to clean my 14 foot LR with elaborate plaster cornices with an extention pole with brushes on it...I purposely did not have any lighting in that ceiling. I think the people who bought the apartment from my buyer put in recessed cans. (Not right in a 1830s house and very hard to change. A ten foot ladder is much harder to manage than an 8 foot ladder).

I'd do some sort of textured natural shade--bamboo, matchstick, grass, etc. Even though some of these treatments have valances or curtain panels, they work very well on their own, as they have attached valances that hide the inner workings. You can have them lined if you want for privacy or blackout purposes, and they come in all manner of colors and materials. They add a nice organic texture to a simple interior.

What did you end up doing? I have a similar problem with an arched window and sloped ceiling. Ideally I wanted a straight curtain rod across the top of the arch but because of the slope I thought it would look funny if drapes didn’t extending the typical 6” or so beyond the window. I’m considering a roller shade or woven shade to cover extending from the top as if it was one large rectangular window but I’m not 100% positive I even have the room for that with my slope. May have to go with two separate shades.....