I love all of the covers for the new Thrawn trilogys, Thrawn alliances especially. The Ahsoka novel and Phasma both have great covers.
The Alphabet trilogy has some neat and bold use of colour in its covers that is matched by the general design of them.
While the book was ok, I really loves Princess and the Scoundrel's cover. It's 1) beautiful and 2) has Leia in the traditional green Corellian wedding dress from the old EU. Also I really like how it incorporates a new planet's setting, something we don't often get on cover art.