That's interesting, and also the first time i've seen an error result from changing the images in the folder. Did you perhaps delete an image that was needed? How did you install this mod? What i would do is restore the images directory to default images, and reunzip the pleasantville mod images into the images folder and try to start, it should work flawlessly.
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Village Monk
"There's no place like 127.0.0.1"