Well, I wouldn't say they're cute... though...
There's two types of ugly, in my opinion:
Bad ugly: Just garish or something. Like a Harlequin looted tank taken too far...
Good ugly: Tyranids. They got wings, and fangs, and claws, and sharp teeth, and various other pointy/acidic/venomous instruments of death...
My Tyranids fall somewhere in between... they end up with lots of stuff sticking to them, but they're painted in pastels... at least they have plenty of bloodstains on them...