I tried to incorporate the points you mentioned and reuploaded the pixel.
Some technical advice....use the darkest green under the white trim of the coat where it would cast a shadow, that will help define the trim and make it pop. Do the same above the white trim on the shoes. You are using a light green in the body but its very close in color to the middle green, make the lighest green even lighter so the contrast is higher. Use this light green as the highlight color on the Grinch's body to create more shape and form. The red highlight on the jacket could also be lighter so it stands out more. This too will create more form. Pay attention to long hard edges and try to avoid them (unless building a house or something). Notice that the red highlight in the hat has a long hard edge at it's bottom, make that edge more curved, so it conforms more to the shape of the hat. Hope this helps.
@Rain Maker: Yeah I know,but it's never too late to be in a holiday mood
@shibumi: thx for your interest
All the points you mentioned are without a doubt valid, but they result from comparing this pixel of the grinch to the artwork i used as preference, I didn't go for a 1:1 convertion.
I'm more interested in technical defects included in my work.
little late on the holidays, but its okay
Love the Grinch. I like where you are going with this. I think the character needs a bit more work, he's not quite on model. I would remove his nostrils and give him a more circular button nose. The Grinch's hat is also kind of skinny and frumpy, yours is a little too large and structured. Your Grinch doesn't seem to have a neck but the character as perceived by Chuck Jones does. I think with a few changes and a little more work your image will really come together.