NASA Monthly Global Images "Blue Marble"

The NASA site at  has monthly satellite images.  It also has a black marble, Night lights image.

Nominal Resolution Actual Resolution (degrees) JPEG Size Upper Left (x, y) Notes
8 km 0.066667 2 MB -180,0  
2 km 0.016667 25 MB -180,0  
500 m 0.004167 8 tiles, 5-40 MB each See readme for file  

Note where you save the file. 

File, Tools Identify directory can create a world file for images of the entire earth, such as this.

Last revision 11/1/2017