try loading the image before you add to the canvas. if you add an image that hasnt been loaded you will get an exception. This works for us:
var img = new Image();
img.onload = function(){
canvas.setBackgroundImage(img.src, canvas.renderAll.bind(canvas), {
originX: 'left',
originY: 'top',
left: 0,
top: 0
});
};
img.src = "your image source"
regards, Benick