btw, I don't change resolutions on my cab...
did you test work? (but just annoyed you?) because it would work great for me

How about forcing the other app to the same resolution (if you know) in mame?
I thought there was a problem displaying graphics or different colors because you don't know what colors are available other then white. Is this still true?
because if you always know that all colors are avaible, I would guess you can load a png file pretty easy (since the library to create it is already there)
So generate a full screen png file before launching each game (if it doesn't already exist)... Then have it pull it up.
But if you go that far. it would be nice to load a snap shoot, cabinet or flyer in game... I can't think of a reason, but once you can get one working... adding another is easy.