*Updated due to vagueness!
Image.php is a new file included in the default theme that comes
with WP 2.5 and that you can use to have a light-weight image gallery built right into your theme,no plugin required.
Image.php uses new template tags to display thumbnails of the next and previous images underneath the one main image. This is something I dearly wanted. Look out for the option (inside the code of image.php) to display the attachment image as small medium or large. I picked large but your theme may not have the space,esp. if you are very naughty and don’t resize your images to a fixed-width-theme-friendly size before uploading them.
This isn’t going to replace a cool gallery plugin like nextGen gallery for me. However it does do something that nextGen doesn’t do, which is provide the option for comments on photos, if that is something important to you. And I’m guessing if you want a photoblog it might be. Although Aniga gallery does let you have comments on individual pictures…but in my one usage of that plugin the comment showed up on the picture thumbnail and looked odd.Anything is customizable and that could be taken care of in the plugin scripts or maybe even the css file. But see? Already too much work! And Aniga may not even work with 2.5, anyway. I’ll report if it does when I upgrade the sites that use it.
I got the heads up from this site in the comments section left by Matt Mullenweg himself.
How to use image.php:
Copy image.php from default theme folder to your theme’s folder.
To make image.php match your theme’s html is easy. Just replace the content,post and entry divs’ names with the ones your theme uses. Most themes all use the same set of div names so you might not need to customize it at all.
In short image.php is the key to not needing to use plugins for your images ever again…but it is kind of basic looking. I’m sure the geniuses are already working on revving it up.
An example of a real live website using image.php.