Hi there Pepijn, welcome to the forum, and pixel art! Your piece actually is quite good for a first work, I have to say, since it doesnt have the blaring pillow shading that most newbies do. Also the colours are reasonably well selected, except for the bright red of the tongue. Also I'm pleased to see you didn't opt for the garish black-outlines that alot of people do.

However, points of critique:
You're using heaps of unnecessary colours/tones! You can cut down alot on the green-tans you are using, as well as some of your red-browns. Try to be very watchful over the colours you are already using, and try not to introduce new colours if there is already a colour present which will do the job.
The image would really benefit from some AA (anti-aliasing). There's loads of tutorials on it which you can find links to in the Support section of this forum. I would really recommend you check them out as it's a very integral skill of good pixel art.
Whilst the shading is not pillow-shading, it still needs considerable work if you want to effectively portray the form of this crazy mushroom. For instance the stem of the mushroom is basically a slightly melted cylinder, so I can't really see why the shadow would curve around the bottom of it like you've done there.
The dithering you've done around the top of the stem doesn't really work. Depending on how close the center of the crown/dome the stem is, there's going to be more shadow casting on the top of the stem, unless you intend on a somewhat upward-pointing lightsource. It's a little ambiguous  for mewhich exact angle the light is coming from at this point.

Uuurgh ok im really tired, I need to sleep. I'll continue my critique in the morning.


Edited by EyeCraft - 14 November 2006 at 9:10am