Before art, perhaps a larger rug more in proportion to room and table with the chairs. Lose the brown chair in the corner - maybe it was a party addition?

The mirror is a bit heavy looking for the sideboard which seems too small for its space. The chandy is hung a bit too high : )

A size appropriate artwork, perhaps a bit coastal on the empty wall or a series .....

Do you love the paint color? Not sure its the best with your flooring, seems to read a bit pink/beige. .....more so with the ice white of trim.

Consider some built in serving /storage in the nice between bookshelves too. Good proportions will lead to less urge to fill corners. Less can be lot more when it is "right sized". NO MATTER the style.

My first thought was 3 large pieces of art, maybe a set that goes together. Another option would be a longer buffet with the mirror over it (it seems a bit large for the wall it is currently on).