I'm working on my wife's Galaxy Tab 2 10.1 running JB 4.1.1 and have copied a dozen or so movies (in mp4 format) to the SD card. The stock/default Video Player (not the Google Play Movies player) seems to display the first frame of each movie as the thumbnail. Of course, this is meaningless because many are black screens, or simply display the movie companies logo, etc. Is there a way to specify the thumbnail image for an mp4 file? I tried creating a JPG to be used as the thumbnail and named it the same name as the mp4 - but this did nothing.