Designing in the browser is cool and all, but starting in Photoshop keeps me at my most creative when I need it the most: when facing the blank canvas. One way to fight against the painful glare of a white canvas is to toss down some texture. We do that here by picking a nice one off Subtle Patterns (they now ship in a @2x version for retina displays, nice!). We take this pattern and make a Photoshop pattern out of it and fill the whole background with it, getting rid of that intimidating whiteness.
The "Big Orange Square" was a fundamental exploration to this entire redesign. We plop it down on the canvas and go from there. We establish the branding in the header that lasts through the rest of the entire process.