VTphotog, are you saying tilt the paintings back 45 degrees to pick up the reflected light?
Yes, approximately 45. Look at it like this: if you lay the artwork flat, you would have to be directly over it to take the picture, and would cast a shadow. If you set the artwork vertically, the lower part will be getting significantly less light. The exact angle used depends on ceiling height, and the room you have to set up in.