To provide a custom background for the logon screen (perhaps to show terms of use etc. e.g. 6030) in Windows, save the following as a .reg file and merge it in to the registry:

Windows Registry Editor Version 5.00
[HKEY_USERS\.DEFAULT\Control Panel\Desktop]
"Wallpaper"="C:\\WINDOWS\\Resources\\Wallpaper\\swirl.bmp"
"TileWallpaper"="1"
"WallpaperStyle"="2"

NOTE: there is no actual image there by default, so you'll need to put one there (it MUST be a bmp file).