Don't lean the mirror. It will just reflect the ceiling. You need a taller lamp for sure. I'd center the mirror over the sideboard, probably add a blown glass bowl or something.

Your sideboard is pretty traditional. I wouldn't put a lamp on it that is too modern.

Try Emily Henderson's gorgeous book titled : Styled. She explains how to do it and explores different styles and combinations of styles. Outstanding, exploding with photos. I found it at the library. You won't be sorry.

It's also available in bookstores.