I recently found a great easy to use photo gallery and edited it to support geeklog. Just upload a directory of images and it will make a gallery of thumbnails that cache, and show within your Geeklog site. It doesn't use any of the plugin api so be sure to read the geeklog_readme.txt for install instructions. You can see a sample of it here. You can download it here. And this is where I got the original scripts Simple PHP Gallery. I would really like to thank the original script author for making such an easy to edit/use script.
http://mentalstout.com/source/article.php/simple_php_gallery_for_geeklog