Search the internet for vintage-style black-and-white Halloween drawings. We used bats, skeletons, witches and old medical drawings. Size the images accordingly, then print them out on the white vellum paper.
Cut the printouts to fit the frame. Place the front of the picture down upon the glass. Cover the back of the paper with the clear packing tape (this way water will not get on the paper and potentially damage it). Lay the packing tape so it overhangs the glass, then fold it over the glass by about 1/4".
Place the glass and print back into the frame and fold the brackets (or nails) back over to hold it all in place.
Lay the four frames down beside each other with the backs facing up (Image 1). Use black tape to secure the edges of the frames together (Image 2). Leave one at the end unattached for the moment. Stand up the frames and put them into a square, then attach the last piece of tape from the inside (Image 3).