How do I change the pre login screen picture on my computer?  This is the screen that appears before I am prompted to enter my login information.

Hi Cullik, 

Thank you for your question. 

We could refer to the following steps to customized login picture: 

1. Launch the Registry Editor by typing regedit into the search box in the Start menu and pressing Enter.In the Registry Editor, navigate to the following key:HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Authentication\LogonUI\Background
2. Youll see an DWORD value named OEMBackground. If you dont see it, right-click in the right pane, point to the New submenu and create a new DWORD value with this name.Double-click the OEMBackground value and set its value to 1.
3. Your image file must be less than 256 KB in size. Its also a good idea to use an image file that matches the resolution of your monitor, so it wont look stretched.Windows looks for the custom logon screen background image in the following directory:C:\Windows\System32\oobe\info\backgrounds By default, the info and backgrounds folders dont exist. Navigate to the C:\Windows\System32\oobe folder and create them yourself by right-clicking inside the folder, pointing to New, and selecting New Folder.
4. Copy your desired background image to the backgrounds folder and name it backgroundDefault.jpg. 

We could also refer to the following link: 

http://blogs.technet.com/b/jamesone/archive/2009/05/07/customizing-the-windows-7-logon-screen-no-additional-tools-required.aspx 

If there are any questions regarding this issue, please be free to let me know. 

Best Regard, 

Jim