Tennogen are usually fans made though. DE only does the pick and choose for what they deemed fitting.
I won't say it is ugly but, yeah I'd wish something some what genteel to fit that dancer. Only that "genteel" is not the defult style of the game to begain with, as the warframes are litterly Infested.
However greneer themed tennogen decal has already be a thing for a long time.
Maybe to the orginal creater this was the safer option. The concept of three faced kuva queen custom is already kinda sick on it's own.
And if you know DE well, their fashion prefferences is not gonna let them miss out something so monstrous and somewhat in “small g - god” likeness. Especially the small g god things, they have a history of taking references upon deities from many religious superstition.
My design to make itself look like a creature on it's own instead of piles of meat or man made construct were for the similar reason.
But, that would spoiler my show, so we might talk about it later some times.