Thanks for the video link anyway, MrGrynch!
In my case it's a bit different - I'm using DMD images in PinballX to display the year of the table in big DMD-style letters.
So my PinballX looks like
Backglass: Animated Backglass video
DMD: Year of the Table
Playfield: Static table image (I found more than one moving image too distracting) with the game's wheel image overlaid.
Since the style of the DMD stays the same, it gives some feeling of uniformity to the menu.
When I start a table I want a video or image displayed that wasn't visible in the PinballX menu before - so I think I'm going to need a PuP-Pack for that.
EDIT: Did it. That was so easy!
Best of all: If I name the DMD video something generic, like "video.mp4", I can just copy and paste the PuP-Pack folder, rename the copied folder to the ROM name I need and swap out the video file. It's perfect! :-D