[gguruusa]

I take it you have a ROM made by someone else, the someone else obviously having used PPCKitchen.org's kitchen. To change the splash, you either need to a) flash someone else's rom that has different splashes, b) make your own ROM using the kitchen (you can choose whatever splash you want - that's just the default), c) flash a .nbh that contains just the splash images you want replaced (you can't change animation with this method).