It would be nice if the hipchat plugin would allow the (new?) card formatting type for message notifications.
These card notifications can be minimized/maximized, include icons and links and much more than was possible with 'simple' HTML messages.

If you'd like to see how one of the cards look like the Jira, Bitbucket interation plugins for HipChat seem to support this already.

This could be used to provide links to the build number, the jenkins server, icons with the jenkins build status, etc.

Please see the API spec for documentation on how the card information needs to be provided.