Mmmmmm.... interesting problem you have there. I'm not sure what to say to correct it other than I know for a fact that Mala will play a video, full screen, with both video and sound before loading up the menu screen(s). I do it everyday with my Mala set up. I too replaced the Windows load up screens with static Jpegs that fit my theme.
I have collected and made several intro videos. All of them play just fine as intro videos. I've never heard of Mala having a problem with this before. The formats I've used successfully are .mp4, .mpg, .mov, and .avi.
A couple suggestions to double check:
Make sure the resolution of your video is not too high. Not higher than the resolution of your set Mala interface for sure. My videos are no bigger than 640x480. My longest/biggest video is only 16 mgs.
Make sure you configure the video to play as an intro in the Mala set-up tab correctly. There is only one section that states exactly that "Intro video" and then you point Mala to the file. Use that function an no other.
Try testing the intro video function with a DIFFERENT video that has been proven to work with other systems.
You can download the ones I made at the end of the post here:
http://www.cheapskategamer.com/pc_game_stories_and_news/building-an-arcade-emulation-cabinetpart-one-software/You might also want to try the videos in the link below. They too will work in my experience:
http://www.cinemarcade.com/movies.htmlAgain, if you can get any of these videos to work, then you know there is something wrong with your created file. Wrong format, wrong size, wrong type of compression settings...something. If the proven videos don't work, then the problem is in your Mala configuration.
Also...if you'd like to see how my Mala frontend works with the intro movie see this YouTube video I made highlighting my cabinet:
Best of luck.