Important notes: Not everyone thinks a cartoon looks the same, cartoons come in many different formats and I try to present some options on this page. This is a technical document and not for general purpose consumption.
ImageMagick++ and GMIC are required. GimpUI is not but Gimp is. Unix is probably required and is recommended.
What I have tried to do is take a normal picture of a primary school kid and treat it so that it is more appealing to the pupil to put on an object of their personal posession.
I have released my findings so if anyone else tries to do the same thing they can:
Simplfied instructions:
Install GIMP-Devel
Install Dependancies for ImageMagick++
Install ImageMagick++
Install Dependancies for GMIC (take note on ftw3)
Install GMIC (takes a long time)
Once GMIC is installed run the commands that I have placed above each example.
You may wish to process this with PHP or Python or so, that should be very simple to do 
GMIC seems to have much lower overheads than ImageMagick++.
Original Image:
GMIC command:
gmic example.jpg -tetris 50 -o example3.jpg
GMIC command:
gmic example.jpg -edges 30 -o example5.jpg
GMIC command:
gmic example.jpg -drawing 30 -o example7.jpg
GMIC command:
gmic example.jpg -stencilbw 20 -o example6.jpg
Yes this looks very weird but if you apply the same effect to the picture of a boy they look like Harry Potter which is pretty cool if your a Primary School kid..
GMIC command:
gmic example.jpg -pencilbw 1 -o example8.jpg