Consider painting your crown an off white. This will give your ceilings the appearance of being higher. Paint all trim the same off white and consider Sherwin Williams Dover white.

If you add ocre to white paint or better naples yellow until the blue is offset with a very light color, you may find it brings a harmony to the blue and offsets the darker ceiling trim. Test it on a large piece of paper first with the color painted to the edge so you get a better idea of your blend's compatibility I have found. It eliminates the surprise element somewhat and can save you time. i also find a week of seeing it put up with masking tape gives me time to digest my decisions, letting the time of day and the effects of nightlighting to sink in so I can decide to add more color or or more white. Good luck!

Repainting the crown isn't really an option though.