How do I fix the wallpaper on my nexus s?

Assuming its on android go to the app store and download "go launcher pro" or "ADW launcher" or any other launcher " ilauncher" all free... and go install it when you press your home key to go back to your home screen you will be prompted to use one of a few launchers use the one you selected ticking the use this option everytime and when your on the home screen you can go into settings and fully customize the way your phone looks and under one of the settings you can select wall paper scrolling... to change the launcher you use you download an app called homesmack which allows you to change the one it loads when you press the home button, this will also solve battery life problems and increase the free ram on your phone as most launchers use less memory than stock... hope that helps