I think the idea is pretty cool, but why do you need so much information (first name, last name, email address, birthday)?

If you just required a username and a password, and then made everything else optional, I think you'd get a lot more signups.

I didn't feel like giving you all that information so I didn't bother creating a login... but if you haven't done it already have you considered adding voting to the pictures? This would be a perfect use-case for the new Facebook "Like" buttons. Thinking about it, maybe Facebook connect would be a good idea as well.

[Edit: You may want to do something better for your privacy policy if you are going to require all this information. Big blocks of "lorem ipsum" text aren't very confidence inspiring. You may also want to change the "you're bound by the ToS when you register" text until you actually have some terms of service.]