Re: advanced posterization

Try this

>Posterize (3 or 4 levels can work, don't care the horrible colors, you'll change them later)

>Median (to soften the borders)

Then make the image inexed color and choose the "custom" palette.

Now the trick:

In the palette window, select the colors from the darker to the middle, then the window to select colors will open two times. Select a dark color the first time and a brilliant one the second time. Now, in the palette window again select from your last brilliant color to the last one. The color selection windows will open again. Leave the first color the same and give the second color a very light color or even white.

Click OK.

If you want you can convert the image to RGB again to fine tune the color.

This is an old trick, from the days indexed color was born, but it still has his uses from time to time. I hope this helps.