HI Andre Jesus.that background is from pakrat2k2 Script have a look at the witcher Script that has been posted by peter that will give u a idea how to change backgrounds in his script.the script i used is from yener which is different.
http://fileforums.com/showthread.php?t=91563 (yener's scripts)
Tutorial :
http://fileforums.com/showthread.php?t=92805 (Yener's Scripts)