D&D 5E - Any New Monsters in the MM?

The empyrean is new, although you can argue that it's a revised titan (classical style).

You could argue that a few of the specific animated objects are new, but that's a pretty wild stretch IMHO.

Other than that, all of the monsters in the MM are classics. It's a pretty good list, too- the only things I'd have replaced are the quaggoth, nothic and homonculus. IMHO there are many far better choices.