Red skull

[Salmeron]

As I only know making small side-scrolling sprites(still newbie too) I tried something different. It's horrible but I still want to fix it.

[Ultimaodin]

Try to use a reference as right now your skull is gradient shaded. Skulls rarely ever have any sort of indication to an eyebrow outside of a more prominent brow which wouldn't create two neat little lines. You could use taking a look at your colours too as it's more a pink than a red at the moment. (almost could be deceived as a dodgy skin colour) The best thing you can do to improve your piece is to study references.

PS I ain't a great pixel artist myself so don't follow my skull completely as mine could also use a lot of improvement just take consideration of the indents and features of a skull.

[Koi Kami Mauro]

Considering how he gave his skull expressive eyes, I really doubt he was going for a realistic skull. Most of Ultimaodin's critiques still stand, though.