Hi Kim,
I'm so glad you put the window back in. It really adds to the moodiness and mystery. This turned out really well! (And the shot on the easel really gives a nice feel for the piece)
For the photography side of things... if you're having trouble getting the camera exactly square and you're shooting with a tripod and your camera has a zoom, the zoom lens can really help to line things up. If you get the camera straight out along the midline of the painting, first you can adjust the side-to-side angle of the camera and check that it's right by zooming in until each of the top and bottom edges of the painting just touch and are parallel with the top and bottom edges of the camera's viewfinder. So now the horizontal angle of the camera is correct. Then you can adjust the vertical tilt of the tripod (adjust the height crank if necessary!) and check it by zooming in until the left and right edges of the painting line up with the left and right sides of the viewfinder frame. . . so now you've got vertical tilt right... Zoom back and forth between the top/bottom and right/left edges to make sure all 4 are square (because sometimes tweaking one messes up the other
Adjust just the zoom to frame the shot the way you want it and take the picture.
(If that's all too much information in this thread, let me know, I'll zap it out!
)