Hey Arnold! Project Heart is a fan project currently being written and designed by deviantART user MrShowtime.
MrShowTime posted several posters of the characters and scenes he made from Hey Arnold!: The Jungle Movie.
The tentative release date for the project is "2015." He wrote about it in his journal saying it's been delayed for time reasons, but he will continue to upload.
You can see more of "Project Heart" at this link.