I want to store images of the world.
Not even google maps is not storing everything into one single picture file
a) you are not able to show the complete picture to the user all in one go (unless you have some very unorthodox video setup using multiple screens).
b) it is much faster to "divide" your map into smaller squares that are easy to handle and compose the current view from several of those squares.
So, what would you like to do with those "images of the world" ? Simply show them on screen/window in a 2d manner ?