Can the Live Media Bar be customized to show the number of chat users/length of time waiting in the queue?
Not version specific, Live Media Bar
Stats can only be displayed in reports. You can customize what the Agent sees in these reports by modifying the Chat Workspaces and Reports. You can also modify the targets for service levels. Below are links to instructions in online documentation on each section relating to this topic:
Chat Configuration (Includes PDF - Best Practices for Implementing Chat)