AGK doesn't have any commands for renaming files or directories.
If you are using Tier 2, you might be able to use the standard file and directory commands to rename things.
But you probably won't be able to change anything in the media directory under the app executable.
New and changed files done with AppGameKit commands, in all platforms, will appear in the appropriate sand box for the platform. For Windows, that is in Documents\AGK\<yourapp>\media.
You can do things like create a new directory, copy the files from the old, delete them from old and delete the old directory. Currently there isn't an AppGameKit copy command. There are lots of versions of functions to do a copy floating about the forum.
Cheers,
Ancient Lady
AGK Community Tester and AppGameKit Master