Full bodied? I can't see his legs! (assuming its a he).

Just kidding, I really like it. Skulls are a little cliche, but I'm voting for this one.

You have a point about the levitating effect, I tryed a propulsor (that ended as the top beam) and glowing ring. But the effect was too recharged.

But finaly I added some smaller propulsion effect. Thanks for the tip.

"So I didn´t care/noticed it." That's perfectly valid reasoning for production art, but on PJ that's likely to make you seem lazy and uncaring, which runs counter to PJ's purpose. PJ is about pixel art where artists put care into every colour and every cluster, which is why so many techniques that are acceptable/common in production art are frowned upon here. Like someone said on the forum in your thread, PJ is a curated gallery, which is different from a portfolio or personal gallery.

To help the it feel more like a vehicle rather than a skull with a weird hat slapped on, I'd recommend adding some visible propulsion. Rocket blasts, levitation/magnetic glowy bits on the bottom, something. Given the level of technology involved it's possible for it to levitate with no visible means, but that doesn't read as well.

The reason I finaly gotten was about the challenge rules "full bodied characters". A floating oversized skull doesn´t count, so I redesigned as a vehicle.

You are right there´s almost one unused color, but it doesn´t surpass the 15 color max spec. So I didn´t care/noticed it.

Thanks for commenting.

You have a grey colour that's almost indisgintuishable from the base purple. How come you opted to use it? I think it'd actually look better to replace it with the purple.

I'm wondering if that's perhaps the reason this piece was sent back at first? Colours like that often pop up when resampling to a smaller palette automatically.