If stick figures figure largely in your unconscious as the beautifully simple reps. of childhood that they are, I advise that you should look at more of them.
Perhaps you see them as simple but beautiful representations of - um -anything. Let's not be too precious about art - it had humble beginnings. From the dawn of time, sticks have been in. For many kids, it's their primary artform.
Sticks and maths? Well no, not really. A stick game is found in a link called Arcade Games on www.funbrain.com . There, you can do a great and silly game using stick drawings. You have to progress through a level (maybe 2?) but it's fun and skill levels are built in.
On top of this, if you want your kids to get some cool things happening with maths and other subjects, this is a good site.
My 10yr and "7 turning 8"yr olds' have approved and given the thumbs up. It's for primary/middle school age kids.
Long live the Stick!