I like the categories and the way the the pictures load bigger in the center of the page.
However I would suggest one change. Your main page is the first thing a person sees, it is what makes their decision to stay and browse or move on to another site.
I would recommend placing less emphasis on who you are and how the site works and more on the pictures and that exist there. More on the experience the visitor can expect if they stay. Basically you need to sell the site.
The picture preload is great and makes the site so much easier to browse.