I'll present to you, the antagonist of this game, Artistico:
Spoiler:

Love the design!

I suppose Artistico will be quite the under-rated, artistic guy who got all riled up with something, so he wants to erase the colors of everything or repaint the world with their own colors and flair.

Would it spoiler if I were to say no, thats not the case, the story is a bit more complicated

I like the general design, but I feel like the head area could use some more personality to it. The base has all these colored stones and what not, then the head is just "Black ball, yellow eyes, hood". Maybe add a border of some sort around the hood? Idk, I mean, it's up to you, I just feel like it's missing something.

thanks for the feedback, I'll tell that the artwork artist ^^

I'm not sure how I feel about Artistico.
The design is all good, but it doesn't strike me as a villain, or even an important person to be honest. He looks like... an NPC, a show moderator or something. His design feels... lacking persoanlity, maybe?

Yeah, it's lacking flair

I agree, the design isn't really screaming "villain" here; he seems more like Chuck Quizmo than say, Dimentio or Antasma. You should probably change the main body from the neutral blue to a more sinister color, like purple, or even pink. I'd also add some angry eyebrows and a sinister grin.

Or you could try something very different from a cloaked ghost, maybe a unique creature, with a paint brush tail or rainbow hair? x)

It is actually not a ghost, its a new species introduced in this game, you know there is a reason why he has a cloak and his face is hidden ^^

p.s. you will also see him in the game without his cloak, but I dont want to spoiler too much

Working on some new Tiles and Backgrounds for the game

This is really good-looking!

Will there be a demo before the final game? Or a sandbox

Oh wow, those backgrounds and tiles look great! Love the unique style to this, looks a lot more interesting than whatever Sticker Star and Color Splash are going with!

I dont want to promise anything yet, but there will be something in the near future

New video is up, it showcases a part of the prologue and how the game will look

I noticed that in the fourth text bubble, "still" isn't capitalized, which should be, since it's the first word in the sentence in that text bubble. The new tiles, backgrounds, and logo look pretty nice, by the way. I like them a lot more than their previous versions.

Oh yeah you're right, gonna change that right away and I'm glad to hear that you like the new "style" ^^

I like that prologue video! However one thing I think would make everything look better, is if Luigi had an animation for when he was sitting down. Without an animation of dangling legs or blinking of the eyes for example, he looks very robotic. Another way to explain it is that Luigi doesn't "breathe" like Mario does... I'm not sure what you would be able to do, but these are my thoughts. It looks like a real Nintendo game! Great job so far!