Did a quick edit of your helmet too Ryan.
Just some tips:
-When doing your lineart, be sure to keep everything smooth and rounded. You do not want jaggies.
-Shading from the outside in is never a good thing (especially with such high contrast)
-Dithering can often ruin a piece and should be done in moderation for small sprites
-Decide on a light source before you start (I use top left) and visualize where light would hit and where shadows would fall.
-Colour can transform a sprite. Choose colors that are easy on your eyes, and that match well with the other colors on your hat.
-Grey looks much better if it is more tinted towards blue or red (in my opinion)
-The whole hat doesnt have to be surrounded in black outlines, use value to show the difference between parts.