You can find info about custom start up/shutdown screens on www.themexp.org plus download custom designs on that site. Here's how you can install a custom log on screen for example:

- Backup (copy) the file %windir%\system32\logonui.exe (most likely C:\windows\system32\logonui.exe - the logon)
- Download the .zip to your computer
- Extract logonui.exe to a directory other than %windir%\system32 (most likely C:\windows\system32)
- Reboot your computer into Safe Mode (hit F8 before the boot screen) or into true DOS (from a boot disk)
- Overwrite the file %windir%\system32\logonui.exe (which should have been backed up) with the extracted exe
- Reboot your computer as you normally would