There was that whole silly "Paul is dead" thing, with people finding various bogus "hidden messages" in the Beatles songs, album covers, etc. The supposed "imagery" on the www.anthrax-letters.com web site is just as meaningless (it's easy for the brain to see patterns that aren't really there, and it's easy for technical artifacts to emerge from an "image enhancement" process).
If you want to see the interesting photos, download the links to TIFF files towards the bottom of the web page. These are apparently high-quality, unmanipulated scans of the FBI photographs of the letters and the envelopes. (These images are not displayed on the page itself; you have to download the images via the links.) These TIFF images are the reason I posted the information on FR.