I like the artistic style and colors of this demon, but many of the lines seem sloppy or hastily drawn.  I recommend you shrink this piece down to about a third of its size, that way you'll have less canvas to cover, and get a better idea of where/how to place your pixels.  So yeah, start smaller.  I think you'll find the anatomy issues are easier to fix that way.

(plus the shading on the horns does not suggest they are round, and could use more contrast and possibly some color, imo)

 It is true that a demon has no defined anatomy, but by making it humanoid, you have set a precedent, and the viewer expects the anatomy to fit the standard to a degree. It is perfectly fine to use artistic license to exaggerate or deform the anatomy, but these changes should be purposeful, otherwise the anatomy just looks unlearned. What is the reason for omitting most of the cranium (which is a common anatomical mistake for beginners)? There is no reason to get defensive toward critique, we critique to help each other, not tear each other down (even if some of us (me) are rather blunt with critique). And if you do want focused critique, we have a WIP forum where users often give better criticism than in the gallery.

Then explain to me how a demon has proper anatomy? o.O And the hairs coming from the back of her head.

no such thing as 'too critical' here. constructive criticism is the name of the game.

A little too critical but meh.

the pixels are accurate now, the pixelling itself has a lot of jaggies. I'd browse through PJ's tutorial and the Ramblethread over at Pixelation to learn more about jaggies/clusters/etc (jaggies are especially bad where the dark grey outlines sit ontop of the white hair, anti-aliasing is the fix to this, or just using a lighter color). the outline of the teeth is actually lighter than the inside of the mouth, which is strange. I would remove outlines entirely in this area. anatomy-wise the cranium is mostly absent. the ears seem to be different sizes, and I'm really uncertain how and where the hair connects to the scalp.

Is that any better? ;/

just click "edit it" beneath the image and replace the files.

Oh right, thanks for the info :) Should I reupload or...?

the preview file cannot exceed 100x100, the actual piece can be any size you want. though we still prefer that previews are not scaled, as they are no longer pixel art after scaling.

Yeah it was 150x150.. but then I realised it had to be 100x100 D:
 

it isn't what PixelJoint would really consider proper, as it seems to be resized. if not resized, then there's a ton of colors and anti-aliasing that has been added by the computer in some way.