Registration page CSS sucks
I was thinking something like this:
Notice that the top of the top text box and the bottom of the bottom text box is rounded, but the bits where they touch aren't rounded. That effect pulled directly from the Bootstrap Signin Template. Also the size of the form. Generally take a look at this template for idea.s
You can get a dual column layout with Bootstrap's grid system and just do a nice login page on the right.
Start with just making the sign up form look good before adding a sign in.