The Skyrim Creation Kit is an application that allows you to develop content for The Elder Scrolls V: Skyrim game. It has several tools so you can create from simple items to more advanced ones. In addition to objects, it is possible to change the faces of characters when creating a character.
The program is a bit difficult to handle at first, but you can find many tutorials on the web that teach you how to use the program. On YouTube there are several video lessons that teach how to use the application.