Customising Image Gallery Themes

The default image gallery as provided by the image gallery module, will displayed in two different ways.

1. If the views module is enabled, it will be displayed as a view.
2. If the view module in NOT enabled, the gallery is output by the module itself.
[If you are using the views module, but would prefer the output to come directly from the image gallery module itself, then just disable the view image_gallery at admin/build/views].

Customing and themeing the image galeries will require two different approaches, depending on how the view is output.

1. Customising the output as provided by the image_gallery module views integration.

The image gallery module provides the following elements to the views module.
A 'Display type': Gallery page
This is similar to the 'Page' display type, and inherits many of its features.
It is a distinct display type, that differs from a 'page' type by inserting an 'image_gallery_terms' view in the header. This allows a mix of nodes [images] and terms [gallery terms] on the same page.

It also provides two default views:
'Image_gallery': This is the actual view of image nodes, displayed in a fluid grid format by default.
'Image_gallery_terms': This isn't meant to be used independently - it is embedded within the 'Gallery Page' display type. This will take subterms and display the first image, count of images, and last updated time. On the top level of image_galleries, this makes up the entire output of the page.

Some elements are provided by the image module itself, and are available for use even without the image_gallery module enabled.

Style plugins
'Gallery' : This is a re-implementation of the Grid style plugin, but not using tables.
'Subgallery List' : This is used by the image_gallery_terms view to display subterms.

Fields: There are a number of fields made available by the image_gallery module, but intended for use with an subgallery list only.

Armed with this knowledge, you can use the views UI to customise your image galleries.

2. Customising the output as provided by the image_gallery natively.

There are a number of theme functions which can overridden in your theme.
These can be found in image_gallery.module file.
See fuller instructions at drupal.org/node/173880.