As an experiment, Matt has turned on custom headers for the plugin directory.

How to add a custom header:

1. Make a 772×250 pixel jpeg or png
2. In the plugin root directory, create a new directory “assets”:

   mkdir assets

   After you’ve created the assets directory, you should have the following directories in the plugin root:

   $ ls -l
   total 0
   drwxr-xr-x  4 per  _www  136 Jan 11 22:19 assets
   drwxr-xr-x  3 per  _www  102 Jan 11 19:57 branches
   drwxr-xr-x  3 per  _www  102 Jan 11 19:57 tags
   drwxr-xr-x  5 per  _www  170 Jan 11 19:59 trunk
   

3. Copy the 772×250 pixel jpeg or png to the assets directory:

   cp my-custom-plugin-header.png assets/banner-772x250.png

4. Add the assets directory to svn:

   svn add assets

5. Check it in:

   svn ci -m 'Adding custom header'

I’ve added a custom header to four of my plugins, please have a look: lorem shortcode, WebPutty Helper, WP-DenyHost and Remove “Comments are closed”.