Skins from MyGelSkin.com & 3ACP.com

3ACP.com has skins for about every device and they are only $5. They also send you a wallpaper to make your bb look seamless. They have *tons* of designs too.
MyGelSkin.com offers a higher quality skin for $22 (but I don't think you get a wallpaper). They have options for about every device except I didn't see them for the 8900.