CustomCover is an Xposed module, inspired by a jailbreak tweak for iOS called CustomCover, that I've always loved. It completely overhauls the Android lockscreen, specifically when playing music. I’ve made it so the album art displays in the center (with an iOS-style look to it), and it can also be themed. The tweak also pulls the prominent colors from the album art of whatever’s playing, and changes the other lockscreen elements to those colors. The end result is an elegant-looking, functional, and fun lockscreen.
I had so many challenges with developing this; every device is different, so it may run fine on one phone, but it has to be adapted for others. I had to constantly fight against and change the way Android fundamentally works, and it was a struggle, to say the least.
Tested only on Stock Marshmallow and CM13, on a Nexus 6P (Stock), Galaxy Note 4 (CM13), and a Galaxy S5 (CM13).