Please see all my comments to the question.
I also found this article about the password being "totally hackable":
http://news.softpedia.com/news/Windows-8-s-Picture-Password-Is-Totally-Hackable-315105.shtml[
^].
Before, in my comments, I actually tried to explain why.
See also the material about the Microsoft patent on this technology:
http://microsoft-news.com/microsoft-patents-windows-8-picture-password-feature/[
^].
This is the patent description itself:
http://www.google.com/patents/WO2012161727A1?cl=en[
^].
If you go in for this, you will have to avoid infringing the patent, which can be quite difficult. But the patent description also suggests that existing Microsoft solution suffers from being between Scylla and Charybdis of ability to recognize the image and to detect imitations, as I awkwardly tried to describe in my comments, which makes it very questionable in terms of false positives and false negatives.
At least it should explain my strong skepticism about the this technology, and even more about the idea of developing of an alternative. I think if you are going to put forward anything at all, it should be very, very different from what Microsoft has. Do you have such ideas?
—SA