The first and the very simple way of doing that, would be the usage of HTML5
element {
background-image: url('../link/to_image.png');
}
Which won't be saved if the user right-clicks the image and clicks Save Image as...But still remember that the user can get the image from Inspector!
This way, the image won't be saved through right click atleast! And your map will be saved.
Second method is to use return of JS and stopping the event from occuring.
$('img').mousedown(function (e) { // mouse down on the image
if(e.button == '2') { // if right click
return false; // return nothing! :)
}
}
This is the easy way, since you won't be require to update the background-image everytime! But, use what you like! :)
