(This article has a real-world perspective)
Photomanipulation is the technique of modifying a photographic image by either analog or digital means. Many Star Trek fan fiction series use photomanipulations of celebrities to represent their characters.
Star Trek: The Farthest Star uses headshots of actors who are placed on bodies and backgrounds in screen captures from Star Trek productions. This is done to add a bit more "reality" and assist the reader in visualising characters.