Riot have said that they wont be doing any more grotesque / Void champions simply because they don't sell as well. The teenagers and girl players would rather buy a hot chick with big boobs than a creature from the void. They consider this kind of champ design "niche". There are a bunch of Xypherous posts about "cute-ugly" champs and why they won't make any more.
Not entirely accurate - and if I've somehow implied this, I deeply apologize for the misunderstanding. Additionally, I can't speak to champion concepting and creation and if we'll make more or not. I'm simply not in charge of or influence those decisions.
The problem with grotesque champions and monstrous ones, in general, is that they have to be personable
. Characters that you can identify with and or relate to as more than 'I am playing scary monster X.'
If a character feels more like something you would kill as a mini-boss than an actual character - that's a problem. It's not an intractable problem - but it does mean these things are a little trickier and we have to put more time on them to succeed. That tends to be why we have a hard time making them - It's easy to make a monster but it's hard to make a monster with personality. Kog'maw does this well, for example, because at his core - he's a puppy's personality.
I recall throughout Nautilus' development - we continuously had to push for more emphasis on the eyes and eye glowing to the point of exaggeration because that was the only part of the character that made him feel like you could resonate with him as a character
in a story - rather than as a monster to be killed.