Because your tablet or smartphone is something you use everyday, Android™ lets you customize your device so it fits your needs.
As a first step, you can change the wallpaper. Described in the following FAQ.
You can also add, move or remove the icons and the widgets to better fit what you do.
In (or) Settings , you will find many customization options such as the interface language, the font size or the different sounds.
For the most experienced users, you can change the default application launcher.This will completely change the look of your system. For instance you can change images of icons or their number per row and column, choose a different transition between each screen change or just add as many home screens as you like.
You will need to install an dedicated app to do this such as the excellent Nova Launcher from Google Play™. You can even apply a Tron theme to Nova launcher :)