The cornice or decorative plaster moulding which runs around the top of your walls were they about the ceiling can be very ornate or as simple as you like.
You can have them handmade and formed in place by craftsmen.
Then there are the pre cast variety made out of plaster and reinforcing off site then attached with glue and the edges filled with filler.
There are even polystyrene cornices. These are very light and meant for the DIY market they don’t look as attractive and are hard to fit well.
Cornice make a very attractive finish to a tiled wall.