Thank you very much for the criticism! I kinda went a little crazy with the dithering, as I just learned how to do it, and I want to see how much it helps. In this case, it makes it look too dirty, as you said. If you look on the forum thread at http://www.pixeljoint.com/forum/forum_posts.asp?TID=19935 , I posted a WIP gif of the two orbs spinning around the pumpkin. The way I do pixel art seems to be too time-consuming and inefficient to be able to produce a piece within a week, as I couldn't get the animation complete in time, but nevertheless it is a learning experience. 

It's not bad at all. I feel that the dithering might actually not help so much here as it gives the pixels a dirtier look. With 16 colors, maybe you could make the color transition smooth without the use of dithering. Just a suggestion. I like your color choice for the shaded part.