Taking a look at WinAjuda I found a great screensavers (screensaver), O Fire Free Screensaver. It simulates the fire consuming your desktop. The animation is very realistic, such as the sound effect of the flames. You can also set the soundtrack, edit the quality of animation and other things. In this website there are other fire-based screensavers, but all are paid.
Click on here to download Fire Free Screensaver.