A common way would be to use a custom renderTarget and just render your current level onto the map.
Of course you could also use a texture but then you’ll need to define your own standard about how many units should be one pixel (If you have a pretty large map you really don’t want it to take up the whole screen).
I suggest you look at this little tutorial. You can obviously also place a static texture instead of the renderTarget if you still feel you have to. 