I have one of these type of 7" displays in my
car pc project. The screen is 16:9 aspect ratio 7" diagonal with VGA or composite inputs. The native resolution is 800x480 pixels. Viewing angle and brightness are good enough that you could VERY easily use this as a custom instruction card or (albeit small) custom marquee.
I am replacing the car screen with a brighter model because it's a little bit dim when sunlight strikes the screen directly, so depending on what I get on my mind to do next, I'll look at appropriating my current screen for use in the mame cab...
The screen also has a touchscreen, so that opens up some possibilities for doing some very very fun things on a mame cabinet. For instance, you could have a tournament bracket program running on the small screen, or you could use it to queue up players with a more high-tech approach than putting your quarters on the monitor glass

*sigh* if I only had the time!