In Windows 7, you can customize your login screen to be any image you want. The Super User blog has a great article on changing the login background screen yourself. I have created several packs with photographs I've taken, already saved in the format needed to use as a Windows 7 Logon Background. You can copy the files and configure it yourself, or run the included install script and everything will be set up automatically.
To install, download the login pack you want using the Download buttons below. Unzip the file, then right-click on Install.cmd and choose Run as Administrator. The script will set up registry to enable custom login backgrounds, then copy over the necessary files. To unzip the file, right-click on the .zip file, then choose Extract All.
A photo I took at sunset in the Sierra Nevada mountain range in California, USA.
Photo I took from Tom McCall Point in the Columbia River Gorge, Oregon, USA.
Photo taken by Audrey Oldenkamp in Istanbul, Turkey. Used with permission.