Background Image setup

Does anyone have instructions on how to take photos to use as background images?
From my experience, I took 3 full body shots from a tripod: Front, Left and Right, if I align the body to size, the head is too small, on the Model, it seems the full body shot may not be to scale, as if I need to take two or more shots and stitch them into one, like a panoramic, since the perspective is from the camera, it seems my camera setup is all wrong, if I take a close up of the head, it seems to work better, but then the head looks to small on the body, seems like a no win situation, I am not sure how to deal with this, anyone have any idea how to take photos that can be used for backgrounds that actually work well, if so can you share your experience on how to setup the shots.
Update:
It seems like I need references lines that might match the lines in MH, not sure what size to make them so the reference markers would work.
From my experience, I took 3 full body shots from a tripod: Front, Left and Right, if I align the body to size, the head is too small, on the Model, it seems the full body shot may not be to scale, as if I need to take two or more shots and stitch them into one, like a panoramic, since the perspective is from the camera, it seems my camera setup is all wrong, if I take a close up of the head, it seems to work better, but then the head looks to small on the body, seems like a no win situation, I am not sure how to deal with this, anyone have any idea how to take photos that can be used for backgrounds that actually work well, if so can you share your experience on how to setup the shots.
Update:
It seems like I need references lines that might match the lines in MH, not sure what size to make them so the reference markers would work.