I use the following image as the desktop background when I log in. I like the blue sky tones suggesting freedom, but when you open the window, there is darkness. Sometimes things are deceptive…

If you would like to have this picture as your background on Windows XP when you log in [it only changes the background while the login dialog is present!], please follow the following steps: [Note: I'm pretty sure this only works if you get a login dialog, not the login screen where you click icons to log in]. If you wish to modify such an icon-based (Fast User Switching) login screen, it is possible to use another tool such as Logon Studio. If you get a logon dialog, the following instructions apply:

1. Download the Magritte.bmp file from here. [You may need to right click on the link and save, see step 2]
2. Save the file in your Windows directory (usually c:\windows), you must have administrative privileges to do this.
3. Download installwallpaper.reg to your desktop (save it there) and double click it. The system will ask if you want to merge the contents to the registry. Click 'yes' to accept. [Verify the contents with a text editor, if you are paranoid, before clicking 'yes']. This will add the image to your background of the login screen, and change the background colour from blue to black. Delete the .reg file from your desktop.
4. To see the image, log off.