Just what the title says! Windows 7 supports the ability to load images into the background of the login screen without the use of third-party software or manual hacks. This excellent tip was published by Rafael Rivera in his "Within Windows" blog. To change the logon desktop background, you just need to complete two simple steps.
(Thanks & Credits to the Within Windows blog.)
Step I – Creating a Registry Value
1. Click Start, type Regedit.exe and press ENTER:
2. Create a new DWORD value named OEMBackground
3. Double-click OEMBackground and set 1 as its value data.
4. Exit the Registry Editor.
Editor’s Note: I’ve observed that it also works if you create the OEMBackground value in the following Policy key:
Use the following Group Policy setting in Windows 7
1. Start the Group Policy Editor (gpedit.msc)
2. Go to the following branch:
3. Set the following option to Enabled
Always use custom logon background
4. Close the Group Policy Editor.
Step II – Include the Wallpaper Image (JPG)
Next step is to place the background wallpaper (JPEG file) in the following folder:
Note that the info folder doesn’t exist by default. You need to create the info and backgrounds folders manually.
Place the background image file (name it as backgroundDefault.jpg) into the above folder.
As for the file naming info and maximum supported file size, check out Rafael’s post Windows 7 to officially support logon UI background customization. Be sure to check out Rafael’s blog for more information and screenshots! And someone even wrote a small utility to change the Windows 7 logon background.