Here are the three historical photos shown in the Fringe episode August (They were also in the Fox press kit for August).
The first image is a photo of Archduke Franz Ferdinand and his wife, which was taken just minutes before they were assassinated, which eventually led to the start of World War I.
The second image is a painting of Marie Antoinette being taken to her execution during the French Revolution.
The third image is an engraving by Paul Revere titled "The Bloody Massacre", which depicts the events of the Boston Massacre of 1770.
If you looked closely at the photos, you should be able to see the Observer in each one, implying that their observations have been going on for a very long time.
As a bonus, I researched these three photos and found the originals: