You have some great photos.
I understand you have the word green in your domain, but I would suggest minimizing the use of green for background color. I think your photos could make the dramatic impact that they deserve if they were set against more neutral colors.
As for navigation, a breadcrumb type navigation would help. As it is, once I click on a photo, the only way to see other photos is to hit the back button. So maybe you can allow people to navigate to next/previous photos when viewing individual photos. In addition to, or instead of, a navigation system so that the visitor can go to the photo's category without using the back button.