Hello there, and yes we actually do care about the number of colors used, 

Yeah the dithering makes it look slightly odd. Sorry I don't have much to say this early in the morning, I mainly posted to say hello to the new person.

Alright, it actually looks like a mushroom now. Even though now its awfully too 2D-looking. :]

I hope someone would give some advice at coloring the outlines, since pure black and dark green / dark gray looks pretty boring...

And hello there greenraven. :p

Still accepting helpful advices. :)

I have to agree with Hatch, go with smooth shading :)

Yes- much better. I say get rid of the "Meep" text. As for colors, make the darkest green a little more blue and the stem yellowish.

Cool. You can put your mushroom under the street lamp. 

The mushroom looks much better than it did at the start but still needs some work. Your lightsource seems to be different in the stem versus how it is in the lower and upper parts of the cap. The rim area of the cap seems shaded best, whereas the top and the stem are just vaguely given light and dark areas. Split the 'shroom into basic geometric shapes and shade, roughly, accordingly; the cap is a cone on a torus, and the stem is a cylinder or cut-off cone with a semisphere on the end. After shading those shapes, you just have to merge them together and tweak based on the more subtle shaping you have in mind.