Pictures would help. But moldings, wallpaper, built ins... all good options.

Molding is always a good solution and there are so many design options to suit most styles.

Appropriately sized art could be nice as well. Imagine below, with art on an upper half-wall. Also consider lighting that draws the eye downward, given the high ceiling.

I think you aren't suppose to. Worry about the room from eye level down..let the rest just be.

Would suggest large, impactful artwork.

I agree, a large art work!