Julia Color Phone is a nice app that has lots of caller screen themes to customize your incoming call screen.If you are not satisfied with your system caller screen,try it.

-Customize your phone’s call screen with our beautiful and colorful themes.
-LED flashes when a phone call comes in.
-Very easy to use,set caller screen and led flash in a few steps
-New themes coming in periodically.
-All themes are free,no points or money are needed.
-Wallpaper:you can customize your homescreen's background with our wallpapers.Phone

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Source: https://play.google.com/store/apps/details?id=julia.color.phone.shine.wallpaper