Windows 7 you'll be getting a simple Login Screen Background, this background is very boring and don't afford a good looking theme after you use it for a long time. Every one who wants to change Microsoft Windows 7 's Login Screen Background just follow this tutorial and get a customized background on your login screen.
How to Change Windows 7 Login Screen Background
1) Go to Start Menu > Type Regedit and hit Enter
2) Registry Editor of Windows will show up:
3) Right Click HKEY_LOCAL_MACHINE and Click Find...
4) The search window will appear, type OEMBackground in the search field.
5) OEMBackground will be found under: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Authentication\LogonUI\Background
If you don't find OEMBackground, go to the folder with the address above and Create a new DWORD value with the same name.
6) Double Click OEMBackground and change its value from 0 to 1 (allow us to change OEM Background)
7) Once completed, go to C:\Windows\System32\oobe or %windir%\system32\oobe
8) Now Create a new folder and name it info (lowercase) and Create inside info a new folder named backgrounds (lowercase), now copy your Background and paste it in backgrounds folder, and Rename it backgroundDefault.jpg
9) Now Restart your Computer or Logout to See your new Windows 7 Login Screen Background.