The first thing I did was overlay a rectagonal grid over an image of an NASA's current estimation of what the Milky Way looks like. After I numbered the grid, this is what I got:
The reason I'm using a rectagonal grid is because the hex grid for sector map found in the SWN Core Rules is 8x9 and there for fits in a rectagonal space. So, since a hex = 1 light year and there are 72 hexes on a sector map, there are just under 109,027,778 sectors in the Milky Way galaxy! (This is a rough estimate figuring the area of the Milky way as a perfect circle with a diameter of 100,000 light years across.) That averages out to just under 2,137,800 sectors per grid section. Each grid section is broken down again in another rectangular grid that is 9x10 call the Major Sectors, like so:
Major Sectors are split into a grid of 72 Grand Sectors, which are then split into 56 Over Sectors, and then finally into groups of 6 sectors called Sub-sectors. This gives each sector it's own numeric code that looks like so: 188.8.131.52.4-(Star Name). Now, sectors that are named won't bother with these codes, but they are there regardless.
That's a lot of sectors, and I could spend the rest of my life mapping them and never scratch the surface, but this gives me a sense of scale. When dealing with the possibilities of over 1 million sectors, a sense of scale is key. (For me at least...)
As for actual sector maps, I'm working on them and hope to have something to share before too long.