You need to explain what you mean by "better"? Why if the right side dropped lower and open? Is this your bathroom or a customers (seeing you are a pro)?

This is a client’s bathroom, not my personal space. My client suggested to try seeking ideas on forums like HOUZZ, so I posted here to gather more perspectives.

We think the mirror here looks not too balance and the right side looks too empty. this space look a bit "boring" .

The lower area is intended to serve as a makeup station, which is why it’s designed at that height and left open for the chair

A bathroom should be a utility room. You need a place for soap by the sink and a hand towel. If the make-up area is to be used for that purpose then a stool needs to tuck under and a lighted magnifying mirror needs to be added (perhaps adjustable off the wall) along with places for hairbrushes and curling/flat irons. Start with the useful things and then it will come together.

How to make it better? Get rid of the depressing battleship gray tile.