artwork question

[mogse]

i have a vertical 19" monitor cocktail cab running space invaders but currently it has no backdrop of the moon like the original. when i put the artwork zip file into the artwork folder of mame it works but makes the whole game very small.
i deleted some of the other image files in the zip like the bezel for instance and just keep the backdrop & .art file.
its makes the game abit bigger without the bezel but its still small.

is their anyway i can adjust the size of the back drop artwork so the whole game fills my 19" monitor screen?
maybe change something in the .art file?


MANY THANKS i'm abit of a newbie