To get a "FULL" featured theme, your ROM needs Theme Chooser (T-Mobile) as a system app. You can try JRummy themes on Google, if you don't have the theme engine to make such system theme changes , then full themes are out. Roms such as AOKP,AOSP, CM, or PAC will already have the theme changer pre-installed. I have MotoInspired (from XDA Developers) running on my HTC One V using Slimbean 3.1 Standard with Apex Launcher setting the Apex Gbox icons. My ROM runs the main theme with Apex managing just the icons. No lag, no problems. All my settings, notice pulldown, calendar, status bar, dialer, etc, are all themed. It all depends on your device, your chosen ROM, and launcher. There's a lot of great themes to choose from, so good luck!