As a budding designer coming from the development side of things, I have to say you did a great job!
I like the large icons that make your options clear despite the non-standard placement of the navigation links.
I also noticed there is a lot of 'help' for users that might not be familiar with how your site works. You even have video demos, very nice!
I'm not sure why, but I feel like I should be using the icon in the top-right of the page somehow. All the icons floating around makes it feel like a navigation panel or something.
On your login/signup page: "Not Registered?" is in the heading. I think some less advanced users might not understand that this is a link to register, or might just miss it completely. I would move the link to somewhere below the form. I would also include the terms "Sign Up" somewhere. For example: "Not Registered? Sign up today!".
Overall I really like this design. It's clean and useable. Well done!