Your only problem will be that you are in Australia, and shipping for small orders will kill most deals.
As to stickers, since the art available in mame is more than satisfactory for small scale work, you could offer prices by the sheet. That way people could just tell you the games they want stickers for, and you wouldn't have to list everything.
It sounds like a very neat service to provide if the quality was good enough. Although I really don't know what I would do with said stickers...

(If we worried about things like that in this hobby, noone would buy anything.)