Startup Screen
Create a 320x400 bitmap in the root directory and name it LOGO.SYS
You can use LOGOW.SYS file in the Windows directory as a starter
Logoff Screens
There are several files called LOGOX.SYS
They are actually bitmaps 320x400 that just have a different extension
The hidden one in the root directory LOGO.SYS is the startup logo.
There are two files in the Windows directory.
LOGOW.SYS is the Wait while Shutting down ... screen
LOGOS.SYS is the You may now shut-off or Reboot screen
To edit them, rename them with a BMP extension and use your favorite graphic editor
You can edit these files or create you own
They just need to be the same size