EPSG Codes

What is the EPSG number used to display the default blank map, that has no features at all on it.
Am creating a slippy map with tiles for a specific area but wish therest of the map to be blank and show just basic map outline with no additions to it at all.

I could be very wrong on this but I think the EPSG numbers are simply codes for various datum/projection combinations to tell the renderer how to convert the internal WGS84 latitude and longitude into a x,y value for display. If you want areas to be blank then you would either block those areas from rendering altogether or assure that the database you are rendering from has only the data you care about.