Have you considered the Drupal framework? For an example, check out http://www.flippr.net/ http://www.flippr.net/ for a Flickr clone that was built in a weekend

Have you considered the Drupal framework? For an example, check out http://www.flippr.net/ http://www.flippr.net/ for a Flickr clone that was built in a weekend. To a great extent, Drupal can be seen as a point-and-click website development kit. Assembling pieces like like the image, watermark, lightbox and other modules like postcard and image notes can provide the pieces you're looking for. Being modular in design, this installation of Drupal could start its life as a simple image gallery but later grow to become a full website with features like an OpenID provider, BitTorrent tracker, Digg-like voting, etc. There's also excellent Menalto Gallery2 integration, but Gallery2 may or may not be what you're looking for.