How to install themes on an Android Phone?

So when dealing with Android, you are right, most manufacturers have their own version of Android. The Nexus phones have the only untouched version as far as I know. If you are wanting a phone that is able to support different "themes" easily I would recommend any of the HTC lineup of Android devices. They are very easy to switch between Themes through the personalization shortcut. Their version of Themes allow you to have a totally different look to your phone whether you are at work, play, or travelling and so on. Most of the live wallpapers work on all phones kind of the same way that you could have the same picture as your wallpaper on all android phones. Live wallpapers sometime use basic phone functions like the G Sensor or even a touch interface, but nothing that would be model specific.