Also one more tip. I've done this for the first android I've ever had. The Samsung Galaxy Prevail. For Boost Mobile. I made several Themes for the a very popular rom called CT-Mod. They were all flashable themes designed for CWM/TWRP based recoverys.
Anyway this phone is very low end.. I believe less than 200MB free 'after' the slimmed down rom. Of course I was too broke to afford an sdcard.. so I uploaded my backups to dropbox. After "enjoying" one rom I'd backup upload flash a new rom.. then redownload. This was ONLY because I was very familiar with this phone and we had Odin's for every version rooted or not.. lol
*So far as the theories of mathematics are about reality, they are not certain; so far as they are certain, they are not about reality.
*Do not worry about your difficulties in mathematics, I assure you that mine are greater. - Albert Einstein (1879-1955)