My first attempt at "Theming" this phone was almost a disaster. Lot's changed since last I messed with modding. Thank Goodness for TWRP & nandroids. I replaced the soft key icons in SystemUI, stripped out an android 6.0 ROM.zip file,put my modded SystemUI.apk in the .zip and flashed it. As I went to boot the phone from TWRP it was kind enough to tell me there was no OS installed, and ask if I really wanted to do that ... haha saved by a nag message! Quick restore and I'm back in business. Guess I got lot's o' learning to do.