Help Wanted: Apples Within

[Shade]

These could be better. The excessive dithering looks ugly and adds little to no depth. Additionally, there's little contrast between the shades, making the characters look even more flat (the green on the porcupine is the most notable offender). Frankly, the colors in general could use some work. When making a palette with green for example, you wouldn't just darken or brighten the green to achieve a proper looking shade or highlight, you would hue shift it a bit, maybe go for a more bluish green as the darker color. This makes the colors more appealing and natural.

The spriting dictionary covers hueshifting way better than I could: http://www.vg-resource.com/thread-25474.html

HUESHIFT- Hue shift, as the name implies, is shifting the hue.

look at this wheel. rather than increasing or decreasing a color's saturation, or its Contrast, you switch to the color to the right or the left on this wheel. Notice also that colors on the exact opposite of the wheel also work as a darker/lighter version of your color. A more dynamic and natural palette of colors is the result of a proper hueshift.
Note: HUESHIFTING can be combined(an to an extent, has to) with CONTRAST and SATURATION in order to produce a wider vaiery of results.
(for an indepth reading on how colors work, read this wikipedia article http://en.wikipedia.org/wiki/Color_theory )

I'd recommend giving the entire dictionary a read. It's an extremely helpful resource for beginners and those more experienced alike.