Yesterday my facebook started showing the pictures in my timeline as a blank white squares. The pictures displayed this way on my linux & windows computers, and android phone because I was using the Comodo Secure DNS IP on my wifi router. My parents who live 3000 miles away are also experiencing the same white blank square on their Facebook page because I installed CIS and used the Secure DNS option.
I switched my router to Open DNS IP addresses and the picture come up fine now.
Something is being blocked by Comodo DNS when accessing Facebook. When I was using Comodo Secure DNS the address of akamai.net would be displayed in the lower left corner of Firefox. I believe Akamai.net is the content distribution network for the Facebook photos.