Need to work on showing images when they are opened in full screen mode. For example, making them fixed on screen also when the user scrolls up/down the page, and maybe improving the popup-mask color with some gradients.
EDIT: a cool popup style: the opened image could be fixed exactly over the gallery box (as it is now), with the black mask behind that fades when it goes over of the gallery box. So, user can scroll up/down without seeing the black mask over the rest of the page.