In Windows 8, you can hide any user from the lock screen. To do this, follow the below given steps:
1) Go to Charms bar –> Search.
2) Type: regedit in Search under Apps.
3) Click on regedit icon on the left side. If you get a dialog box asking “Do you want to allow the following program to make changes to this computer?”, click on “Yes”.
4) In the Registry Editor, go to: HKEY_LOCAL_MACHINE –> SOFTWARE –> Microsoft –> Windows NT –> Current version –> Winlogon
5) Right click on Winlogon and select “Key” under “New”. Right click on this newly created key and select “Rename”. Rename this key as: SpecialAccounts.
6) Now, right click on SpecialAccounts key and click on “Key” under “New”. Name the new key as: UserList
7) Then, right click on “UserList” key and select “DWORD (32-bit) Value” under “New”. Create the DWORD (it will be created on the right side of Registry Editor).
8) Right click on the DWORD and select “Rename”. Rename it as the same name of the account which you wish to hide from the lock screen.
9) When you are done, close Registry Editor.
That’s it. You have just hidden a specific user account from the lock screen in Windows 8. When you login to Windows 8 the next time, you will not see this account in the lock screen. To hide more users, create a DWORD again and rename it to the name of the account. If you wish to show the accounts again in the lock screen delete the DWORD.