Thanks go to the WPEngineer.com guys who posted this article about a new feature coming up in Wordpress 2.9 (due for release sometime this year!)
In WordPress 2.9, there will be the ability to add an image to a post, as it’s been known of magazine themes. The image need not be insert into the post. With the new feature the_post_image() you can use the new feature and thus control where to display.
You can read the rest of the article on wpengineer.com.
It’s a very useful idea as it’s the kind of thing I keep putting into themes I make but I have to use various custom fields and other bits of code. I’m looking forward to it.