So I have a Samsung Galaxy S2 and its the only Android phone I have ever had, and when I first got it I liked the phone and I heard it was a really good phone at the time but I really hated the look of the software. Because of this I tried multiple different launchers like Apex, Nova, GO and so many others but I couldn't get the status bar, notification menu, system settings panel and all the other system stuff to change. I then had one of my good friends root and flash a new ROM onto my phone (SlimBean 4.1.2) and the staus bar, notification menu, system settings panel.... all changed to a much better look, much cleaner and much more 'stock androidy' but I'v never really thought it looks that great.
My question is, could I hyperthetically change how the status bar as well as all the other system features of the phone looks by changing the ROM? Is it the ROM's that manifacturers develop to make there phones look different from one another, TouchWiz to Sense for example?
How hard is it to make your own looking ROM if that is the case because I will be getting the HTC One but I want the software to look as 'fashionable' as the phone does, as clean and eligant as iOS 7?