WinterBoard

WinterBoard is a file replacement extension for iOS using Mobile Substrate, both of which are developed by saurik. It is often used for theming GUI elements, such as app icons. See saurik's website for more information.

It works by injecting replacement files dynamically but without actually replacing the files, though it appears to the iPhone that the files have been replaced. Should SpringBoard crash, the files will no longer appear to be the changed ones, except for a few images that iOS caches, such as the Notification Center and app switcher backgrounds.

WinterBoard themes are installed to /Library/Themes.

saurik has mentioned that he may not update Winterboard for iOS 7 depending on if it has people helping to update as he does not want to update it himself.