How to add or change themes on your Android device: complete customization guide, including latest CM7 themes

Introduction:

One of the frequently asked questions about Android devices is how do you change theme, or use one of the themes available in the Android Market. This guide will explain what are the different types of themes, and how to use each type.
Type of themes are:

• App themes
• Launcher themes
• ROM themes (old)
• ROM themes (new)

Other sorts of customization will also be covered. 

App themes

App themes are built into individual apps. They should be more accurately described as "color schemes". Usually, there are only two variations: white on black (i.e. dark theme), or black n white (i.e. bright theme). For example, Appbrain has both a white or black theme built into the app. It can be changed from within the app's preferences.
However, some apps go a lot further. Some SMS apps like Handcent SMS or Go SMS allow you to configure how the SMS "conversations" will appear. Type of icons, placement of the "bubbles" or dialog boxes, list or conversation style, and so on are possibilities. However, these may just be part of preferences, not as an overall "theme".
App themes in general controls the "borders" of the dialog boxes, the colors of the buttons and the input fields, any icons and bitmaps (including backgrounds) used in the app, and notification icons (if any). They are restricted to within the app itself.
It is not possible to add themes to existing apps unless there is some sort of capability built into the app. For example, Go Contacts and Go SMS have themes for their specific apps. Other apps may have this capability as well, but it must be built into the app.  Handcent SMS also has themes, but they chose to call it "skins".
If the app offers no ability to theme, it may be possible to find "hacked versions" of the app that has different looks, if it is a popular app. For example, HTC_IME, a popular Android soft keyboard, has several "mod" versions to fit with different color schemes. However, these are hacked copies of the original app, so you cannot load two of these at the same time. You have to uninstall the original to put in the "hacked" copy, and due to the dubious nature of these hacked copies, they are not widely distributed. You can often find them on XDA-Developers.

Launcher Themes

Android's default "desktop" is called either Home or Launcher. The default one is pretty plain, and there are many different home replacements available. (over 50 at last count) Furthermore, many of the home replacements allow you to load "themes packs".
The prominent home replacements that accept themes are

• ADW.Launcher / Ex
• Live Home
• GO Launcher Ex
• Launcher Pro Plus (Paid only / widgets only)
• Open Home
• Panda Home

The theme packs you find on Android market usually belong to one of these home replacement apps (unless they are "CM7 themes" which will be discussed later). The theme packs are generally not cross-compatible, and are only for that specific app.
These themes in general replaces the app icons both as shortcuts and within the app drawer. Some launchers also allow replacing the "drawer" trigger button, add a background behind the app icons, and so on. There may also be an included background / wallpaper. Actual change of the app drawer function, such as changing the grid density, change the scroll from up/down to left/right, and so on would be based on the launcher itself, not the theme pack.
How to load the theme depends on the app itself. In general, you install the theme like an app, then you should be able to go into the app's preferences and find the appropriate section to apply the theme. The only except is LauncherPro Plus, where each widget can have its own theme, so you have to apply the theme for individual widgets.

ROM themes (old)

ROM themes (old) requires manually patching the "resources" file within the system area, which means the phone must be "rooted". There are two ways generally to do this:

• Rom Manager
• Metamorph (and its cousin Ninjamorph)

You can find instructions on how to use each just below.
ROM themes, being a part of the system, affect ALL parts of the system, including notification bar color schemes, system notification icons (the ones to upper right, like battery, 3G, etc.). They can be overridden by Home-level or App-level themes though.
WARNING: If you patch the files the wrong way (wrong version, wrong phone, wrong ROM, etc.), you will corrupt the files, which would require a reflash or recovery to regain phone function. ALWAYS make a backup first and know how to restore it! How to do so is beyond the scope of this hub, but search for ROM Manager and Nandroid should get you started.

http://www.youtube.com/watch?feature=player_embedded&v=xhtc88fhyBc