trouble setting up image planes

Ok. For days I have been stuck on this problem. I can't figure it out. I select camera, I create 3 image planes, a top, a front and a side. I load the images of the car into each plane. I go to rotate the top image plane 90 degrees on the Y axis and I get the message, "Warning: Could not find an appropriate startup camera: top. A substitute will be used.". It the changes my top view to my front view. So I basically have 2 front views, a side and a perspective view. I already started the model but It's making it very difficult. Any idea what I'm doing wrong please?