The last few days have been spent reviewing and revising the results I obtained with unpaper in March of last year. After double-checking the image output, I found I had missed some cases where unpaper had failed to properly process the images. After applying the appropriate command-line options discussed previously, I was able to get unpaper to correctly process most of these; the rest I added to the list of images which unpaper cannot process. I also double-checked this list, which originally had 142 images; I found that many of them were able to be processed successfully with a little more command-line option experimentation.
In the end, there was a net increase of seven images to the list, so it now contains 149 images. These cases are almost exclusively pages with illustrations (usually cover pages). I will now have to do some preliminary tests to determine whether it would be more efficient to crop these images manually or use my autocrop tool.