Jonesy - 3:51 pm on May 19, 2010 (gmt 0)

Are these truly JPEG's -- with associated JPEG EXIF data?
If so, you might get away with simply comparing the first 512
(or even 256) bytes if each image file, Or, the MD5SUM of that
section.

That's the method I've used in the past to check for new, updated
images from remote web cams.