Here is a cheap little project that gives good results and is easy enough for kids to enjoy.

Step 1: Material

For this project, you will need...
A picture you like
A computer with a printer
Glue stick (good quality)
Painting material
Foamboard or cardboard

Step 2: Adjust Brightness and Contrast

With an image treatment program (I used paintshop pro) adjust the brightness and contrast of your image until you have a black and white, low detail picture. Print it on good quality paper (cheap paper will wrinkle when painted)

Step 3: Stick It!

Stick the picture to a foamboard or a cardboard piece, and choose two high contrast paint colors. If you plan on using a mix of two colors, I suggest you make a big quantity of it because it`s hard to mix exactly the same color twice. If your darkest color is lighter than black or brown, you should also print the picture in gray and white instead of black and white, since the black of the ink is going to show through the paint.

Step 4: Start Painting!

1.First, cover the large black areas with the darkest color. Avoid the details and the edges of the faces.
2.Then, give an extremely light coat of the lightest color over the face. It doesn`t matter if the color is not uniform at this point.
3.Start painting over the details with the darkest color. Don't paint unflattering lines, like big creases, blemishes, unibrows, and giant moles. You can also embelish the picture as you wish, trimming off a milimeter or two of the contour of a face to make it slimmer, or elongating eyelashes and adding details to hair. The nice thing with paint is that you can`t go wrong! You can always correct a shaky line or a blotch by adding another coat of color.
4.Once you painted over all the details, put on a second (and probably third and fourth) layer of the palest color to hide the original picture and to make the color uniform.