I wonder if it is an Easter egg (as they call them) alluding to Olivia's trip to the other Universe. I think someone mentioned it a long time ago perhaps in the Fringe board but I hadn't thought about it for a long time. Thanks for reminding me of it. Just another layer to be sought out from the episodes. I wonder how many more 'Easter eggs' there are that we haven't noticed or commented on.

I found the pics I posted in my usual place but brightened it up as the original was very dark. Home - Fringe Files