CyanogenMod 12.1

Smooth, stable, pure android, fully working ROM made by CyanognMod team. This is ROM, what are you looking for if you are bored with Z500s stock KitKat and want to upgrade. Themes support, additional features like customizable clock, battery icon and other tweaks. 

Carbon ROM 5.1.1

Super smooth, CyanogenMod 12.1 based custom ROM with good battery backup, good RAM management, lots of features and more, this is Carbon ROM made by Carbon developers.

BlissPOP 4.0.3

The most elegant custom ROM on this page  made by the best developers out of there. BlissROM keeps everything nice and tidy by embedding all of our features within the settings dialog, and not making them all seperate apps that clutter your app drawer. Welcome to BlissPOP.

MoKee OS 5.1.1

MoKee OS is an intuitive aftermarket Android firmware. Unleash the creative side of you, customize how your phone looks; make it cool, make it colorful! With MoKee OS unique battery saving strategies, get the most out of your phone's battery.

OctOS 6.0.1 AOSP

Smooth, stable, fully working, a lot of customizations, one of the best ROMs I have ever tested. The ROM had to be something we’d run, reliable, and customization by the user to the level of their desire. OctOs is an Android Open-Source Project utilizing Android 6.0.1 (AOSP) and CyanogenMod code bases.

Resurrection Remix 5.5.9

Finally presenting you Resurrection Remix 5.5.9. Smooth, stable, fully working, fucking fast, with a lot of customizations and the best ROM I have ever ported. This awesome ROM is made by Resurrection Remix team