Using RDP, you get a max number of sessions (2). If you try and connect to a session, given the right group policy settings, you get the "Reconnection" screen:
Windows Logon
Select a session to reconnect to
You already have active remote desktop connections on this company
-> Session loggin on for X days and Y hours
Disconnected for Z minutes
-> Session loggin on for X days and Y hours
Disconnected for Z minutes
Is there a way to change the information about the sessions displayed on this window? I'd like to be able to show the source IP/Computer that the sessions are under.
On W2K8R2 you can run Remote Desktop Services Manager (which is available in Administrative Tools even without the RDS role installed) and connect to any other server. Once connected to the appropriate server you can right click a session and select Status from the context menu to see the status of the session, including the client name and ip address.
As for your actual question, I don't know of any setting to change what you want.
Maybe not quite what you're after, but RDCMan has baked in functionality to see what sessions are logged on to a server and where from (just right click on a server and choose List Sessions).
It's a pretty neat replacement for the RDP client built in to Windows too, and I find it invaluable when you've got more than a couple of servers to look after.