Due to a recent change from Google regarding their Image Search system, the build-in cover-search feature of MoviePlayerApp is currently non-functional.
We are aware of the issue and working on a solution as quickly as possible.
However, it is still possible for the app to display cover images, but they will need to be added manually, in the same location as where your video file is located.
This article describes the steps (along with screenshots and a sample file) in detail:
But in short, it is simply a matter of saving a jpg file with the same name as the movie in the same location:
(the _bg.jpg file is optional, and if used will result in MoviePlayerApp displaying a background image as well as a cover image when browsing your movies)