It looks like you're new here. If you want to get involved, click one of these buttons!
Android is a unique os. Apart from features, it is the only OS that you can customize anything in it to your needs.
here is what to do.
1- If you use a stock ROM:
You can download a launcher (I recommend Nova Launcher), an Icon pack (choose whatever you like, there are a lot), go to the settings of the launcher and choose Icon pack, then select your desired icon pack).
Also there are widgets (lots of them, but I recommend zooper widget), not to forget some of them are customizable.
2- If you use a custom ROM with a bulit in theme choser (like CyanogenMod)
Aside from the mentionned above, there are some themes on the play store (check compatibility first), so you can customize your system's UI. And a bonus of having a theme engine, is that you can download several themes, and apply one to each specific UI item (like system apps UI, icons, sounds, boot animation...etc)