This is one of those great ideas I found on Pinterest. This link leads right back to the post at The Twice Remembered Cottage that describes how they did it - which is slightly different, because they built their own frame.
I got this giant piece of sheet metal at the hardward store, and cut it down to the right size with tin snips. Because my frame was so big (about 2' x 3'), this piece was pretty expensive ($20, I think), but since it was the only thing I purchased for this project, I was okay with it. Smaller pieces of sheet metal are much less expensive.
I tore pages out of an old book. Some of them I faux aged with a tea bag. To do this, I got the tea bag wet, and used it like a paintbrush across the pages. I let the pages dry overnight. Then, I sprayed spray adhesive on the metal, small sections at a time, and set the pages down, smoothing them with a credit card type card.
You can see how some of the pages are darker color than the others, from the tea. I trimmed around the edge of the metal, to cut off the pages that were hanging off the edge. I also sprayed over the pages with clear sealer - though I don't know if it needed it. I made sure all my edges were sealed well with the spray adhesive, so I probably could have gone without the clear spray over the top. It added spots that look perpetually wet, so I don't know if I would recommend it.
Here it is with a few magnets. I was thinking it would be fun to use to hold a reading chart in the summer, what with the book pages as a background :)
Or, it is pretty darn cute holding my daughter's rainbow princess picture...