Ok. Here's how to change the logon background
How to change logon screen background in Home and Pro
1. Click Start > click Run > type regedit > and click OK.
2. Navigate to the following registry key:
HKEY_USERS\DEFAULT\Control Panel\Desktop
3. In the details pane (right-side), double-click the Wallpaper string value item.
4. In Value data , type the path and name of the picture or background, and then click OK .
IMPORTANT: Make sure that you specify the path correctly to the Background. And that it is a Bitmap!
You have now changed the logon Background.
This will take effect when you logoff.
Or here are a few third party tools to do it.
http://logonloader.danielmilner.com/http://logonloader.danielmilner.com/Logon loader will do it for the logon page, not sure about the logoff.
Style XP is also a good solution, and it does themes too.
Hope it helps
-Goz