Developing Image Authentication Control

I just start developing another ASP.NET Control that allows users to authenticate via text rendered on a image.

This is my Goal:

OK, this is very regular way to implement this kind of control, so I was thinking of the future extention:

KittenAuth is interesting approach to increase the security level. It shows a buch of pictures and a user selects which one looks like purr animal. In version 2.0, it is mixing the kind of animals too.

By: gavi on: