I've seen in many places that people try to theme Tap Tap Revenge (AppStore version) and it goes all wonky and people get the "Tap Tap Revenge cannot be opened" message. Here's how to do it right:

I'm going to use this theme as an example on how I did it. Adjust accordingly for other themes.

1. Download Winterboard

2. Make these folders:
/Library/Themes/theme-name/Bundles/com.tapulous.TapTap/(all the images from the Tap Tap.app folder from the theme go here)
/Library/Themes/theme-name/Bundles/com.tapulous.TapTap/Aweso.ttrTheme/(images from Aweso.ttrTheme folder from the theme go here)

3. Apply the theme in Winterboard.

I've read somewhere that the reason it doesn't start up with the moving Tap Tap.app to /Applications method is that when you open the app, Apple (or your device) checks each file in the app to make sure it's signed and official. When you put these Guitar Hero and Rock Band .pngs into the AppStore version of Tap Tap (which checks for all the images to be signed), your device sees the images are in fact not signed and therefore doesn't run the app. (I'm not sure whether this is true but it sounds plausible to me).

Here's the Guitar Hero Mod folder that I use if you don't want to do everything manually.
Guitar Hero Mod.zip

Just unzip the "Guitar Hero Mod" folder and drag it into /Library/Themes and apply with Winterboard.

Questions? Comments? Praise?