ExtendedPrivateMessaging

ExtendedPrivateMessaging adds additonal features to Special:Chat, including easily-accessible group private messaging and alerts when users block and unblock you.

The screenshot shows the group PM creation screen, that dims the whole page (but doesn't render it unusable) except the help tooltip and userlist. You can also see in the background the (configurable) icon used for group private messages, and modified header to include all members.

Installing
Add the following to your wiki's MediaWiki:Chat.js or your personal chat.js. Or if you already have an  call you can add this:

Customization
All variables are stored in the  object, which must be defined before the importArticles statement.
 * groupIcon
 * This is a string of a publicly available image to be used in place of the first avatar in the group list. Please keep this image to 30px in height and width.

Example: