If you've ever wondered how to make your ROM beautiful, you have probably looked into theming. Creating themes is genuinely hard work, and requires theme authors to spend hours drawing and resizing images to keep their work beautiful. This same work is done by OEMs, which hire graphics designers to provide some of the highest quality images in their stock firmwares.

XDA is a hacker community, and as such, practically everything that has been developed for a device can be extracted for use on another. If you've been looking to theme your Android navigation soft keys, XDA Recognized Contributor neXus PRIME has an Xposed Framework module that you may find interesting. NeXus Navbarz allows you to modify the navigation buttons on the bottom of your screen.

This module features a long list of included navbars, and it will surely be expanded in future releases. You should be able to use the module with all AOSP-based ROMs, and users have reported success with Xperia firmwares as well. Since it's an Xposed module, installation is very easy. Just apply the module, select your favorite navbar style, reboot and voilà! Your ROM looks totally different.

You can find the module in its original thread.