In android lock screen acts as screen saver. If you want to use any other animation as screen saver in place of default lock screen, try about how to create custom lock screen ?
If you are looking for screen saver of normal PCs, you have to modify/create the Home Screen App to add this screen saver feature. I think no concept of screen saver till android 2.3.3. I don't know about after 2.3.3.