Android offers unlimited choice. You can change your background. You can add widgets. You can change your keyboard, icons, launcher, battery display, and pretty much everything is customizable. Your device is even more customizable if it is rooted and running a custom recovery. You can run a custom rom which changes the entire UI of your device. Now you can install apps from different OEMs to your device thanks to an app called PortedAPP. The app is a compilation of some or the most popular OEM apps from Samsung, Nokia, Sony, MIUI, and CyanogenMod. The apps have been ported to work with Any Android device. You will obviously need to enable unknown app sources for this to work. Head to the link below for the download.
Via XDA