This annoyance has popped up off and on for years. You initiate a Remote Desktop connection to a system over VPN and the login screen has a large bitmap image causing it to draw and redraw while you wait.
This is typical for Windows Storage Server 2003 on Dell hardware. Unfortunately there isn't a GUI setting for this, so it 's just better to search for the file and delete or rename it. In this case it's: C:\Windows\System32\dellwall.bmp which is 3MB, no wonder it takes time to draw over a slower connection.