casey talks about picture CAPTCHAs in a recent blog. What about putting various pictures on the same jpg. Let's say a hat, cake, drum, jar, spool of thread, rocket, etc. All things that have very similar signatures. Have the app randomly rotate and place each item all over the picture and draw random numbers on them. You would also use colors that make edge detection more difficult. Then you ask the user "What number is that hat?" further "What do you get if you add the hat and the rocket?" Any thoughts?