I cannot for the life of me set up the 3D view of the character with the camera, whenever I move within the camera view I lose the background image. I cannot see how I am supposed to do this, I need help as when I then try to sculpt nothing correlates between the side view and the 3D view of the robot. As well as the mirror modifier only works on the Z axis for some reason.
Background Images are actual objects now, they have more possibilities, but need a little bit of a different approach.
Go into Camera View. SHIFT+A > Add Image > Background Image. SHIFT select the Camera and CTRL+P > Set Parent to Object.
I'd need at least a screenshot to see what's wrong with your Mirror Modifier.