It looks like it pulls data from the "backdrops" section on TMDb. See the movies.io page[0] for a movie and its corresponding[1] TMDB page. There's also a TMDb API method to get a list of all the relevant images in XML[2].
TMDb's TOS states that you can't "Use TMDb APIs in any manner or for any purpose that violates any law or regulation, any right of any person, including but not limited to intellectual property rights, rights of privacy, or rights of personality."
How does this reconcile with your use for a torrent search engine?
Congrats on building a beautiful product too.