there is must be something not right somewhere, because I just tried on my side and the following is perfectly working :
me.game.world.addChild(new me.ImageLayer(0,0, {image:"cityscene"}), 1);
and cityscape is the name of an png image with the src set to "data/img/cityscene.png"
Are you sure, the path to the image is correct, and that the image is properly returned by your server ? Else, can you share your example, because just like this I have no clue why it's not working.