The 'fifth wall' has a great potential to make your room feel dramatically different. Depending on how much natural light comes into your bedroom, you could paint the highest point one color, and paint the lower flat area, another.

I have seen tray ceilings paint the vertical 'walls' of the tray or keep them white. It may take some experimenting to see what you personally like.

I like how the tan/brown look in this ceiling, may be an option for your bedroom with the yellow/and maybe a neutral brown?



Here are more ceiling ideas:

http://www.houzz.com/ideabooks/query/ceiling%20color