@Gecimen - I normally do more advanced illustrations http://luneder.artstation.com/ so as long as there is feedback it should not take me long to catch up to monster pixel artists on here.
@Gecimen - yeah I need to play with texture some more, this one was mostly an experiemnt with using only 16 colors. The horn I didn't notice until you pointed it out but I forgot to put that rim light on to better place light direction.
I just did a quick edit to it just now to give it some texture by changing how the values blend. Also added the rim light that was missing on the horns.
The desing is great, maybe you could play with the colour pallete.
While the lineart of the sprite looks good I'll have a few criticism about the filling.
Horns defy the lightsource and are pillow shaded.
Also your red tones are mostly at the same hue which makes them plastic-y and boring.
The lineart within the sprite can be better blended with appropriate antialiasing. Same goes for the inner sides of outer lines. The rib lines are especially too rigged.
If you want to gain skill in pixel art, I advise you to use the forums both in www.pixeljoint.com and www.wayofthepixel.net