Howto implement navigation

Include all photos for a tag in show.html, but mark only 20(?) as visible.
Javascript buttons to switch to next/previous 20 photos which hides the current ones and displays new.
Performed with style=display:none and a fake img src attribute (the thumbs should not be pre-loaded) (perhaps construct the img src from the a href attribute?).

Show bigger image inline as a "pop-up" with next/previous buttons that traverses the current DOM tree to select image. Image details are loaded using AJAX.