If you want to create a new theme to the photo gallery you should follow these steps:
- Create a new directory under the themes directory in the installation directory with the name of your theme
- Create two directories under your theme directory: css and pics
- The css directory should hold a file called gallery.css (and a file called admin.css in version 2.x). Easiest way is to copy them from an existing theme directory but you can also create them from scratch. Edit the css-files according to your own preferences.
- The pics directory should hold at least one file: dummy.gif which is used to represent a blank image in the image administration page. This image should have the same dimensions as the thumbnail dimensions stated in the settings file. You can also put other images in here for your own theme (backgrounds etc)
- Change the theme setting in the settings.php file to point to your new theme (it should be the same as the name of your newly created theme directory)