How to change themes in iphone
1. Open Installer or Cydia, go to All Packages, and then install "Summerboard" (Version 3.0 if you’re on 1.1.1 or 1.1.2; or, “Summerboard Old” if you’re on firmware version 1.0.2). Restart your iPhone. Summerboard is a program that will let you download themes and change your iPhone’s wallpaper.
2. Next, launch Summerboard (the icon reads SMBPrefs) from your Springboard. Go to Theme, and select one of the provided themes. If you want to use the theme wallpaper, go to Theme Wallpaper and change the box to "kaha On". Otherwise, your chosen wallpaper will be your background.
3. Within Installer or Cydia, if you go to >Themes(Summerboard) and you will see a long list of cool looking themes
4. Install any themes and then restrart your iphone.