Help with listing

[gnuttisch]

Anyone have suggestions on how to solve the molding against the sloping ceiling here in the nicest way? Is it a corner strip against the ceiling molding that's needed?

 

[gnuttisch]

In the inner corners I've solved it like this

 

[Testarn]

Up towards the ceiling in the niche, I would place the same trim as in the other inner corners.

To finish the paneling at the outer corner, I would cut away 8-10 mm from the panel and attach a wooden trim that aligns with the wall and the panel, which would then be stained/glazed in the same white as the panel or painted in the same color as the wall. This is just to cover the end grain.
I would plane down the outer corner of the trim to a small radius to make painting easier.