Warren began working as a freelance illustrator during his final years leading up to graduating from St Martins in London. Shortly after, he was approached by a costume department at Pinewood Studios headed up by Colleen Atwood for the movie Sweeney Todd: The Demon Barber of Fleet Street , directed by Tim Burton.
Warren debuted as a concept artist with Colleen Atwood and went on to produce work for Alice in Wonderland, Dark Shadows, Snow White and the Huntsman, Miss Peregrine's Home for Peculiar Children’ and Fantastic Beasts. Mission Impossible 5:Rogue Nation, Pan, Disney’s Maleficent, Beauty and the Beast are also some of the other productions that Warren worked on. In between jobs Warren built up a body of work also for film and tv production campaigns and currently works as a concept artist within this field in New York.